Gas generating compositions

ABSTRACT

The present application provides a gas-generating aqueous fluid containing a gas-generating compound like an azo compound, and an organic amine like a primary, secondary or tertiary amine, a hydrazine, a hydrazide, or a semicarbazide. The aqueous fluid may also a viscosifier, and a foaming surfactant. The present application also provides a method of using the gas-generating composition to modulate density of a wellbore fluid for use in downhole applications. The method optionally includes adding an oxidizer to the wellbore fluid.

CLAIM OF PRIORITY

This application is a divisional of and claims the benefit of U.S.application Ser. No. 16/282,245 filed on Feb. 21, 2019. The entirecontents of the previous application is incorporated herein byreference.

TECHNICAL FIELD

This disclosure relates to aqueous fluids containing a gas-generatingcompound that may be used in wellbore applications.

BACKGROUND

Recoverable fluids, such as hydrocarbons (for example, petroleum,natural gas, combinations of them) and water, are frequently found insubterranean formations. Production of a recoverable fluid from asubterranean formation often requires drilling onto the subterraneanformation to produce a wellbore through which the recoverable fluid isbrought to the surface. Wellbore fluids such as drilling fluids, carrierfluids, fracturing fluids, spotting fluids, cementing fluids, completionfluids, stimulation fluids, remedial fluids and clean-up fluids are usedin the wellbore to perform multiple functions, such as preventing thefluid influx from formation into the wellbore, removing drill cuttingsand debris from the wellbore, perforating the casing, primary cementing,fracturing of the subterranean formation for increased recoverable fluidproduction, cleaning wellbore surfaces, sealing fractures andmicroannuli within and around the cement sheath, consolidatingincompetent subterranean formations, and the like.

SUMMARY

Use of a conventional wellbore fluid having constant viscosity anddensity may lead to certain disadvantages. In one example, suddenchanges in formation type and formation strength may lead to varyingfracture gradients leading to loss of circulation. In another example,when residual drilling fluid is left behind casing in a completed well,the casing may be susceptible to collapse from sustained casing pressure(SCP) or annular pressure buildup (APB) due to the fluid expansionbehind casing. Also, use of a conventional cementing fluid may lead topoor compressibility of set cement to sustain cyclic stresses, poorcement-to-casing bond, and to formation of microannuli. Therefore,issues associated with the wellbore fluids can reduce well productivityand increase well maintenance costs.

In some embodiments, the present disclosure provides an aqueousgas-generating composition containing a gas-generating compound (forexample, an azo compound or an organic amine compound). In one example,the composition may be prepared ahead of a wellbore operation. Thecomposition can be stored until the time it is needed. In anotherexample, the composition may be prepared immediately before the wellboreapplication. A liquid injection pump can be utilized to inject thegas-generating composition into a wellbore treatment on-the-fly in acontinuous operation. Alternatively, the gas-generating composition canbe batch mixed into a wellbore fluid. The composition can then beactivated, for example, by adjusting pH of the wellbore fluid, adding anoxidizer immediately before pumping the fluid downhole, or both.

In some embodiments, the present disclosure provides a gas-generatingaqueous composition comprising an azo compound of Formula (I):

or a salt thereof, where:

-   -   X¹ and X² are each independently selected from C₁₋₆ alkyl, C₂₋₆        alkenyl, C₂₋₆ alkynyl, OR^(a1), and NR^(c1)R^(d1);    -   each R^(a1), R^(c1), and R^(d1) is independently selected from        H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, and        C₆₋₁₀ aryl; and    -   an organic amine.

In some embodiments of the compound of Formula (I):

-   -   X¹ and X² are each independently selected from OR^(a1) and        NR^(c1)R^(d1); and    -   each R^(a1), R^(c1) and R^(d1) is independently selected from H        and C₁₋₆ alkyl.

In some embodiments, the azo compound is azodicarbonamide:

or a salt thereof.

In some embodiments, an amount of the azo compound in the aqueouscomposition is from about 1 wt. % to about 10 wt. %.

In some embodiments, the organic amine is a primary, secondary ortertiary amine of Formula (IVa):

or a salt thereof, where:

-   -   R^(n1), R^(n2) and R^(n3) are independently selected from H,        C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7 membered heterocycloalkyl,        each of which is optionally substituted with 1, 2, or 3        substituents independently selected from hydroxyl, C₁₋₆ alkoxy,        amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and        carbamyl; or    -   any two R^(n1) and R^(n2), or any two R^(n2) and R^(n3), or any        two R^(n1) and R^(n3) together with the N atom to which they are        attached form a 4-7 membered heterocycloalkyl, which is        optionally substituted with 1, 2, 3, 4, or 5 substituents        independently selected from C₁₋₆ alkyl, NH₂—C₁₋₆ alkylene,        OH—C₁₋₆ alkylene, hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino,        di(C₁₋₆ alkyl)amino, carboxy, and carbamyl.

In some embodiments of the amine compound of Formula (IVa):

-   -   R^(n1), R^(n2) and R^(n3) are independently selected from H and        C₁₋₆ alkyl, which is optionally substituted with 1, 2, or 3        substituents independently selected from hydroxyl, C₁₋₆ alkoxy,        amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, and carboxy.

In some embodiments, the organic amine is a hydrazine compound ofFormula (IVb):

or a salt thereof, where:

-   -   R^(n4), R^(n5), R^(n6), and R^(n7) are independently selected        from H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7 membered        heterocycloalkyl, each of which is optionally substituted with        1, 2, or 3 substituents independently selected from hydroxyl,        C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,        carboxy, and carbamyl; or    -   any two R^(n4) and R^(n5), or any two R^(n6) and R^(n7),        together with the N atom to which they are attached form a 4-7        membered heterocycloalkyl, which is optionally substituted with        1, 2, 3, 4, or 5 substituents independently selected from C₁₋₆        alkyl, hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆        alkyl)amino, carboxy and, carbamyl.

In some embodiments of the hydrazine compound of Formula (IVb):

-   -   R^(n4), R^(n5), R^(n6), and R^(n7) are independently selected        from H and C₁₋₆ alkyl, which is optionally substituted with 1,        2, or 3 substituents independently selected from hydroxyl, C₁₋₆        alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, and        carboxy.

In some embodiments, the organic amine is an ethyleneimine compound ofFormula (IVc):

or a salt thereof, where:

-   -   n is an integer from 1 to 10,    -   R^(n8), R^(n9), R^(n10), and R^(n11) are independently selected        from H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7 membered        heterocycloalkyl, each of which is optionally substituted with        1, 2, or 3 substituents independently selected from hydroxyl,        C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,        carboxy, and carbamyl; or    -   any two R^(n8) and R^(n9), or any two R^(n10) and R^(n11),        together with the N atom to which they are attached form a 4-7        membered heterocycloalkyl, which is optionally substituted with        1, 2, 3, 4, or 5 substituents independently selected from C₁₋₆        alkyl, NH₂—C₁₋₆ alkylene, OH—C₁₋₆ alkylene, hydroxyl, C₁₋₆        alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy,        and carbamyl.

In some embodiments of the ethyleneimine compound of Formula (IVc):

-   -   n is an integer from 1 to 8, and R^(n8), R^(n9), R^(n10) and        R^(n11) are independently selected from H and C₁₋₆ alkyl, which        is optionally substituted with 1, 2, or 3 substituents        independently selected from amino, C₁₋₆ alkylamino, di(C₁₋₆        alkyl)amino, carboxy, and carbamyl.

In some embodiments, the organic amine is a hydrazide compound ofFormula (IIa) or Formula (IIb):

or a salt thereof, where:

-   -   R¹ is selected from H, C₁₋₆ alkyl, C₆₋₁₀ aryl, and —NH—NH₂,        where said C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3        substituents independently selected from C₁₋₆ alkyl, hydroxyl,        amino, C₁₋₆ alkoxy, and NO₂; and    -   R² is selected from H, C₁₋₆ alkyl, carboxy, carbamyl, C₁₋₆        alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl, aminosulfonyl, C₁₋₆        alkylaminosulfonyl, and di(C₁₋₆ alkyl)aminosulfonyl.

In some embodiments of the hydrazide compound of Formula (IIa) orFormula (IIb):

-   -   R¹ is selected from C₆₋₁₀ aryl and —NH—NH₂, where said C₆₋₁₀        aryl is optionally substituted with 1, 2, or 3 substituents        independently selected from C₁₋₆ alkyl and NO₂; and    -   R² is selected from H, carboxy, carbamyl, and aminosulfonyl.

In some embodiments, the organic amine is selected from: carbohydrazide,p-toluenesulfonyl hydrazide, hydrazine, triethanolamine, ethylenediamine, tetraethylene pentamine (TEPA), diethyletriamine (DETA),triethylenetetramine (TETA), and polyethyleneimine, or a salt thereof.

In some embodiments, an amount of the organic amine in the compositionis from about 1 wt. % to about 10 wt. %.

In some embodiments, the composition comprises a foaming surfactant.

In some embodiments, the composition comprises a viscosifier.

In some embodiments, pH of the composition is from about 4 to about 9.

In some embodiments, the present disclosure provides a method ofmodulating density of a wellbore fluid, the method comprising adding agas-generating aqueous composition of the present application to thewellbore fluid.

In some embodiments, the method comprises adding to the wellbore fluid acomposition comprising an oxidizing compound.

In some embodiments, the oxidizing compound is selected from: aperoxysulfate, a peroxycarbonate, a peroxyborate, a peroxide, ahypochlorite, and an organic peracid.

Unless otherwise defined, all technical and scientific terms used herehave the same meaning as commonly understood by one of ordinary skill inthe art to which the present application belongs. Methods and materialsare described here for use in the present application; other, suitablemethods and materials known in the art can also be used. The materials,methods, and examples are illustrative only and not intended to belimiting.

Other features and advantages of the present application will beapparent from the following detailed description and figures, and fromthe claims.

DETAILED DESCRIPTION

Accordingly, the present application provides a composition containing agas-generating compound and an activator compound. This composition cangenerate gas (for example, N₂) on-demand, for example, after addition toa wellbore fluid and pumping the fluid downhole. Examples of embodimentsof such compositions, and methods of making and using thesecompositions, are described here.

Definitions

As used in this application, the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.

As used in this application, the term “about” means “approximately” (forexample, plus or minus approximately 10% of the indicated value).

As used in this application, the term “room temperature” refers to atemperature of about 15° C. to about 28° C.

As used in this application, the term “standard temperature andpressure” refers to 20° C. and 101 kPa.

As used in this application, the term “compressibility” refers to ameasure of the relative volume change of a fluid as a response to apressure. The term compressibility describes the ability of a fluid tobe compacted (made more dense). For example, fluid may be 10 v/v %, 20v/v %, 30 v/v %, 40 v/v %, or 50 v/v % compressible. An incompressiblefluid cannot be compressed and has relatively constant volume anddensity throughout.

As used in this application, the term “azo compound” refers to acompound containing an azo group of formula —N═N—.

As used in this application, the term “hydrazide compound” refers to acompound containing a hydrazide group of formula —C(═O)NHNH— or—S(═O)₂NHNH—.

As used in this application the term “semicarbazide compound” refers toa compound containing a semicarbazide group of formula —NHC(═O)NHNH—.

As used in this application, the term “oxidizing compound” refers to achemical substance that has the ability to cause other substances tolose electrons. Examples of oxidizers include oxygen, hydrogen peroxideand the halogens.

As used in this application, the term “carbamyl” refers to a group offormula —C(O)NH₂.

As used in this application, the term “C_(n-m) alkylcarbamyl” refers toa group of formula —C(O)—NH(Cn-m alkyl), where the alkyl group has n tom carbon atoms.

As used in this application, the term “di(C_(n-m)-alkyl)carbamyl” refersto a group of formula —C(O)N(C_(n-m) alkyl)₂, where the two alkyl groupseach has, independently, n to m carbon atoms. In some embodiments, eachalkyl group independently has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “aminosulfonyl” refers to a groupof formula-S(O)₂NH₂.

As used in this application, the term “C_(n-m) alkylaminosulfonyl”refers to a group of formula —S(O)₂NH(C_(n-m) alkyl), where the alkylgroup has n to m carbon atoms. In some embodiments, the alkyl group has1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “di(C_(n-m) alkyl)aminosulfonyl”refers to a group of formula —S(O)₂N(C_(n-m) alkyl)₂, where each alkylgroup independently has n to m carbon atoms. In some embodiments, eachalkyl group has, independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “C_(n-m) alkyl”, employed alone orin combination with other terms, refers to a saturated hydrocarbon groupthat may be straight-chain (linear) or branched, having n to m carbons.Alkyl moieties include, but are not limited to, chemical groups, forexample, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl,isobutyl, sec-butyl; higher homologs, for example, 2-methyl-1-butyl,n-pentyl, 3-pentyl, n-hexyl, 1,2,2-trimethylpropyl, and the like. Insome embodiments, the alkyl group contains from 1 to 6 carbon atoms,from 1 to 4 carbon atoms, from 1 to 3 carbon atoms, or 1 to 2 carbonatoms. The term “C_(n-m) alkylene” refers to a divalent alkyl group.Examples of alkylene groups include ethan-1,1-diyl, ethan-1,2-diyl,propan-1,1,-diyl, propan-1,3-diyl, propan-1,2-diyl, butan-1,4-diyl,butan-1,3-diyl, butan-1,2-diyl, 2-methyl-propan-1,3-diyl, and the like.

As used in this application, “C_(n-m) alkenyl” refers to an alkyl grouphaving one or more double carbon-carbon bonds and having n to m carbons.Example alkenyl groups include, but are not limited to, ethenyl,n-propenyl, isopropenyl, n-butenyl, sec-butenyl, and the like. In someembodiments, the alkenyl moiety contains 2 to 6, 2 to 4, or 2 to 3carbon atoms.

As used in this application, “C_(n-m) alkynyl” refers to an alkyl grouphaving one or more triple carbon-carbon bonds and having n to m carbons.Example alkynyl groups include, but are not limited to, ethynyl,propyn-1-yl, propyn-2-yl, and the like. In some embodiments, the alkynylmoiety contains 2 to 6, 2 to 4, or 2 to 3 carbon atoms.

As used in this application, “C_(n-m) cycloalkyl” refers to non-aromaticcyclic hydrocarbons including cyclized alkyl or alkenyl groups.Cycloalkyl groups can include mono- or polycyclic (for example, having2, 3 or 4 fused rings) groups and spirocycles. Ring-forming carbon atomsof a cycloalkyl group can be optionally substituted by 1 or 2independently selected oxo or sulfide groups (for example, C(O) orC(S)). Also included in the definition of cycloalkyl are moieties thathave one or more aromatic rings fused (for example, having a bond incommon with) to the cycloalkyl ring, for example, benzo or thienylderivatives of cyclopentane, cyclohexane, and the like. A cycloalkylgroup containing a fused aromatic ring can be attached through anyring-forming atom including a ring-forming atom of the fused aromaticring. Cycloalkyl groups can have 3, 4, 5, 6, 7, 8, 9, or 10 ring-formingcarbons (C₃₋₁₀). In some embodiments, the cycloalkyl is a C₃₋₁₀monocyclic or bicyclic cyclocalkyl. In some embodiments, the cycloalkylis a C₃₋₇ monocyclic cyclocalkyl. Example cycloalkyl groups includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclopentenyl, cyclohexenyl, cyclohexadienyl, cycloheptatrienyl,norbornyl, norpinyl, norcarnyl, adamantyl, and the like. In someembodiments, cycloalkyl is cyclopropyl, cyclobutyl, cyclopentyl, orcyclohexyl.

As used in this application, “heterocycloalkyl” or “aliphaticheterocycle” refers to non-aromatic saturated or unsaturated monocyclicor polycyclic heterocycles having one or more ring-forming heteroatomsselected from O, N, or S. Included in heterocycloalkyl are monocyclic4-, 5-, 6-, 7-, 8-, 9- or 10-membered heterocycloalkyl groups.Heterocycloalkyl groups can also include spirocycles. Exampleheterocycloalkyl groups include pyrrolidin-2-one,1,3-isoxazolidin-2-one, pyranyl, tetrahydropuran, oxetanyl, azetidinyl,morpholino, thiomorpholino, piperazinyl, tetrahydrofuranyl,tetrahydrothienyl, piperidinyl, pyrrolidinyl, isoxazolidinyl,isothiazolidinyl, pyrazolidinyl, oxazolidinyl, thiazolidinyl,imidazolidinyl, azepanyl, benzazapene, and the like. Ring-forming carbonatoms and heteroatoms of a heterocycloalkyl group can be optionallysubstituted by oxo or sulfido groups (for example, C(O), S(O), C(S), orS(O)₂). The heterocycloalkyl group can be attached through aring-forming carbon atom or a ring-forming heteroatom. In someembodiments, the heterocycloalkyl group contains 0 to 3 double bonds. Insome embodiments, the heterocycloalkyl group contains 0 to 2 doublebonds. In some embodiments, the heterocycloalkyl group is unsaturated(for example, the heterocycloalkyl contains at least one double bond).Also included in the definition of heterocycloalkyl are moieties thathave one or more aromatic rings fused (for example, having a bond incommon with) to the non-aromatic heterocycle, for example, benzo orthienyl derivatives of piperidine, morpholine, and azepine. Aheterocycloalkyl group containing a fused aromatic ring can be attachedthrough any ring-forming atom including a ring-forming atom of the fusedaromatic ring. In some embodiments, the heterocycloalkyl is a monocyclic4-6 membered heterocycloalkyl having 1 or 2 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur and having one or moreoxidized ring members. In some embodiments, the heterocycloalkyl is amonocyclic or bicyclic 4-10 membered heterocycloalkyl having 1, 2, 3, or4 heteroatoms independently selected from nitrogen, oxygen, or sulfurand having one or more oxidized ring members. In some embodiments, theheterocycloalkyl is a 8-12-membered heterocycloalkyl (for example,bicyclic heterocycloalkyl). In some embodiments, the heterocycloalkyl isa 8-16-membered heterocycloalkyl (for example, bicyclic or tricyclicheterocycloalkyl). In some embodiments, the 8-12 membered bicyclicheterocycloalkyl is a 8-12 membered fused heterocycloalkylaryl group ora 8-12 membered fused heterocycloalkylheteroaryl group. In someembodiments, the heterocycloalkyl is a 9-12 membered bicyclicheterocycloalkyl. In some embodiments, the 9-10 membered bicyclicheterocycloalkyl is a 9-10 membered fused heterocycloalkylaryl group ora 9-10 membered fused heterocycloalkylheteroaryl group. The term“heterocycloalkylene” refers to a divalent heterocycloalkyl linkinggroup.

As used in this application, the term “aryl,” employed alone or incombination with other terms, refers to an aromatic hydrocarbon group,which may be monocyclic or polycyclic (for example, having 2, 3 or 4fused rings). The term “C_(n-m) aryl” refers to an aryl group havingfrom n to m ring carbon atoms. Aryl groups include, for example, phenyl,naphthyl, anthracenyl, phenanthrenyl, indanyl, indenyl, and the like. Insome embodiments, aryl groups have from 6 to 10 carbon atoms. In someembodiments, the aryl group is phenyl or naphthyl.

As used in this application, the term “hydroxyl” refers to a group offormula —OH.

As used in this application, the term “carboxy” refers to a —C(O)OHgroup.

As used in this application, the term “C_(n-m) alkoxy”, employed aloneor in combination with other terms, refers to a group of formula—O-alkyl, in this application the alkyl group has n to m carbons.Example alkoxy groups include, but are not limited to, methoxy, ethoxy,propoxy (for example, n-propoxy and isopropoxy), butoxy (for example,n-butoxy and tert-butoxy), and the like. In some embodiments, the alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “amino” refers to a group offormula —NH₂.

As used in this application, the term “C_(n-m) alkylamino” refers to agroup of formula —NH(alkyl), in this application the alkyl group has nto m carbon atoms. In some embodiments, the alkyl group has 1 to 6, 1 to4, or 1 to 3 carbon atoms. Examples of alkylamino groups include, butare not limited to, N-methylamino, N-ethylamino, N-propylamino (forexample, n-propyl)amino and N-isopropylamino), N-butylamino (forexample, n-butyl)amino and tert-butyl)amino), and the like.

As used in this application, the term “di(C_(n-m) alkyl)amino” refers toa group of formula —N(alkyl)₂, in this application each alkyl groupindependently has n to m carbon atoms. In some embodiments, each alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms. Examples ofdialkylamino groups include, but are not limited to,N,N-methylehtylamino, N,N-diethylamino, N,N-propylethylamino,N,N-butylisopropylamino, and the like.

As used in this application, the term “C_(n-m) alkylcarbonylamino”refers to a group of formula —NHC(O)-alkyl, in this application thealkyl group has n to m carbon atoms. In some embodiments, the alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “C_(n-m) alkylsulfonylamino”refers to a group of formula —NHS(O)₂-alkyl, in this application thealkyl group has n to m carbon atoms. In some embodiments, the alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “aminosulfonylamino” refers to agroup of formula —NHS(O)₂NH₂.

As used in this application, the term “C_(n-m) alkylaminosulfonylamino”refers to a group of formula —NHS(O)₂NH(alkyl), in this application thealkyl group has n to m carbon atoms. In some embodiments, the alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “di(C_(n-m)alkyl)aminosulfonylamino” refers to a group of formula—NHS(O)₂N(alkyl)₂, in this application each alkyl group independentlyhas n to m carbon atoms. In some embodiments, each alkyl group has,independently, 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “aminocarbonylamino”, employedalone or in combination with other terms, refers to a group of formula—NHC(O)NH₂.

As used in this application, the term “C_(n-m) alkylaminocarbonylamino”refers to a group of formula —NHC(O)NH(alkyl), in this application thealkyl group has n to m carbon atoms. In some embodiments, the alkylgroup has 1 to 6, 1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “di(C_(n-m)alkyl)aminocarbonylamino” refers to a group of formula —NHC(O)N(alkyl)₂,in this application each alkyl group independently has n to m carbonatoms. In some embodiments, each alkyl group has, independently, 1 to 6,1 to 4, or 1 to 3 carbon atoms.

As used in this application, the term “hydroxy sulfobetaine” refers to amoiety of formula:

or a salt thereof. In some embodiments, a salt of the hydroxysulfobetaine moiety is the sodium salt. The squiggly line represents asurface to which the hydroxyl sulfobetaine can bind.

The term “downhole” as used in this application refers to under thesurface of the earth, for example, a location within or fluidlyconnected to a wellbore.

As used in this application, the term “drilling fluid” refers to fluids,slurries, or muds used in drilling operations downhole, for example,during the formation of the wellbore.

As used in this application, the term “stimulation fluid” refers tofluids or slurries used downhole during stimulation activities of thewell that can increase the production of a well, including perforationactivities. In some examples, a stimulation fluid can include afracturing fluid or an acidizing fluid.

As used in this application, the term “clean-up fluid” refers to fluidsor slurries used downhole during clean-up activities of the well, forexample, any treatment to remove material obstructing the flow ofdesired material from the subterranean formation. In one example, aclean-up fluid can be an acidification treatment to remove materialformed by one or more perforation treatments. In another example, aclean-up fluid can be used to remove a filter cake (mudcake).

As used in this application, the term “fracturing fluid” refers tofluids or slurries used downhole during fracturing operations.

As used in this application, the term “completion fluid” refers tofluids or slurries used downhole during the completion phase of a well,including cementing compositions.

As used in this application, the term “remedial treatment fluid” refersto fluids or slurries used downhole for remedial treatment of a well.Remedial treatments can include treatments designed to increase ormaintain the production rate of a well, for example, stimulation orclean-up treatments.

As used in this application, the term “cementing fluid” refers to fluidsor slurries used during cementing operations of a well. For example, acementing fluid can include an aqueous mixture including at least one ofcement and cement kiln dust. In another example, a cementing fluid caninclude a curable resinous material, for example, a polymer that is inan at least partially uncured state.

As used in this application, a “carrier fluid” refers to any suitablefluid for suspending, dissolving, mixing, or emulsifying with one ormore materials (solid particular materials) to form a composition. Forexample, the carrier fluid can be at least one of crude oil, dipropyleneglycol methyl ether, dipropylene glycol dimethyl ether, dipropyleneglycol methyl ether, dipropylene glycol dimethyl ether, dimethylformamide, diethylene glycol methyl ether, ethylene glycol butyl ether,diethylene glycol butyl ether, butylglycidyl ether, propylene carbonate,D-limonene, a C₂-C₄₀ fatty acid Ct-Cm alkyl ester (for example, a fattyacid methyl ester), 2-butoxy ethanol, butyl acetate, butyl lactate,furfuryl acetate, dimethyl sulfoxide, dimethyl formamide, a petroleumdistillation product of fraction (for example, diesel, kerosene,naphthas, and the like) mineral oil, a hydrocarbon oil, a hydrocarbonincluding an aromatic carbon-carbon bond (for example, benzene,toluene), a hydrocarbon including an alpha olefin, xylenes, an ionicliquid, methyl ethyl ketone, an ester of oxalic, maleic or succinicacid, methanol, ethanol, propanol (iso- or normal-), butyl alcohol(iso-, tert-, or normal-), an aliphatic hydrocarbon (for example,cyclohexanone, hexane), water, brine, produced water, flowback water,brackish water, and sea water. The fluid can form about 0.001 wt. % toabout 99.999 wt. % of a composition, or a mixture including the same, orabout 0.001 wt. % or less, 0.01 wt. %, 0.1, 1, 2, 3, 4, 5, 6, 8, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97,98, 99, 99.9, 99.99, or about 99.999 wt. % or more.

As used in this application, the term “fluid” refers to liquids andgels, unless otherwise indicated.

As used in this application, the term “subterranean material” or“subterranean formation” refers to any material under the surface of theearth, including under the surface of the bottom of the ocean. Forexample, a subterranean formation or material can be any section of awellbore and any section of a subterranean petroleum- or water-producingformation or region in fluid contact with the wellbore. Placing amaterial in a subterranean formation can include contacting the materialwith any section of a wellbore or with any subterranean region in fluidcontact with the wellbore. Subterranean materials can include anymaterials placed into the wellbore, for example, cement, drill shafts,liners, tubing, casing, or screens; placing a material in a subterraneanformation can include contacting with such subterranean materials. Insome examples, a subterranean formation or material can be anysubsurface region that can produce liquid or gaseous petroleummaterials, water or combinations of them. For example, a subterraneanformation or material can be at least one of an area desired to befractured, a fracture or an area surrounding a fracture, and a flowpathway or an area surrounding a flow pathway, in this application afracture or a flow pathway can be optionally fluidly connected to asubterranean petroleum- or water-producing region, directly or throughone or more fractures or flow pathways.

As used in this application, “treatment of a subterranean formation” caninclude any activity directed to extraction of water or petroleummaterials from a subterranean petroleum- or water-producing formation orregion, for example, including drilling, stimulation, hydraulicfracturing, clean-up, acidizing, completion, cementing, remedialtreatment, abandonment, and the like.

INTRODUCTION

In general, the disclosure provides various gas-generating compositions.Such compositions may be added to a wellbore fluid, and may generate gasin the wellbore fluid thereby modulating density and compressibility ofthe wellbore fluid. Such compositions typically contain an azo compoundand an organic amine, and optionally a viscosifier, a foaming or foamstabilizing surfactant, at least one additional ingredient, or anycombination thereof. To aid in gas generation, an oxidizing compound mayalso be added to the wellbore fluid. Various embodiments of the azocompounds, organic amines, viscositiers, foaming or foam stabilizingsurfactants, oxidizing compounds, additional ingredients, as well astheir amounts in the gas-generating compositions, are described later.

Examples of Azo Compounds

In some embodiments, an azo compound has Formula (I):

or a salt thereof, where:

X¹ and X² are each independently selected from C₁₋₆ alkyl, C₂₋₆ alkenyl,C₂₋₆ alkynyl, OR^(a1), and NR^(c1)R^(d1); and

each R^(a1), R^(c1), and R^(d1) is independently selected from H, C₁₋₆alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, and C₆₋₁₀ aryl,where said C₁₋₆ alkyl is optionally substituted with C₆₋₁₀ aryl.

In some embodiments, X¹ is selected from C₁₋₆ alkyl, C₂₋₆ alkenyl,OR^(a1), and NR^(c1)R^(d1). In some embodiments, X¹ is selected fromC₁₋₆ alkyl and C₂₋₆ alkenyl. In some embodiments, X¹ is selected fromOR^(a1) and NR^(c1)R^(d1). In some embodiments, X¹ is C₁₋₆ alkyl. Insome embodiments, X¹ is C₂₋₆ alkenyl. In some embodiments, X¹ isOR^(a1). In some embodiments, X¹ is NR^(c1)R^(d1).

In some embodiments, X² is selected from C₁₋₆ alkyl, C₂₋₆ alkenyl,OR^(a1), and NR^(c1)R^(d1). In some embodiments, X² is selected fromC₁₋₆ alkyl and C₂₋₆ alkenyl. In some embodiments, X² is selected fromOR^(a1) and NR^(c1)R^(d1). In some embodiments, X² is C₁₋₆ alkyl. Insome embodiments, X² is C₂₋₆ alkenyl. In some embodiments, X² isOR^(a1). In some embodiments, X² is NR^(c1)R^(d1).

In some embodiments, X¹ and X² are each independently selected from C₁₋₆alkyl and C₂₋₆ alkenyl. In some embodiments, X¹ and X² are eachindependently selected from OR^(a1) and NR^(c1)R^(d1). In someembodiments, X¹ is C₁₋₆ alkyl and X² is C₂₋₆ alkenyl. In someembodiments, X¹ is C₁₋₆ alkyl and X² is OR^(a1). In some embodiments, X¹is C₂₋₆ alkenyl and X² is OR^(a1). In some embodiments, X¹ is C₁₋₆ alkyland X² is NR^(c1)R^(d1). In some embodiments, X¹ is C₁₋₆ alkyl and X² isNR^(c1)R^(d1).

In some embodiments, X¹ and X² are each C₁₋₆ alkyl. In some embodiments,X¹ and X² are each C₂₋₆ alkenyl. In some embodiments, X¹ and X² are eachOR^(a1) and the compound of Formula (I) has Formula (Ia):

or a salt thereof.

In some embodiments, X¹ is OR^(a1), X² is NR^(c1)R^(d1), and thecompound of Formula (I) has Formula (Ib):

or a salt thereof.

In some embodiments, X¹ and X² are each NR^(c1)R^(d1), and the compoundof Formula (I) has Formula (Ic):

or a salt thereof.

In some embodiments, R^(a1) is selected from H, C₁₋₆ alkyl, C₂₋₆alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, and C₆₋₁₀ aryl. In someembodiments, R^(a1) is C₆₋₁₀ aryl-C₁₋₃ alkylene. In some embodiments,R^(a1) is H. In some embodiments, R^(a1) is C₁₋₆ alkyl. In someembodiments, R^(a1) is C₂₋₆ alkenyl. In some embodiments, R^(a1) is C₃₋₇cycloalkyl. In some embodiments, R^(a1) is C₆₋₁₀ aryl.

In some embodiments, R^(c1) and R^(d1) are independently selected fromH, C₁₋₆ alkyl, and C₂₋₆ alkenyl. In some embodiments, R^(c1) and R^(d1)are independently selected from H and C₁₋₆ alkyl. In some embodiments,R^(c1) and R^(d1) are each H. In some embodiments, R^(c1) and R^(d1) areeach C₁₋₆ alkyl. In some embodiments, R^(c1) are each H and R^(d1) isC₆₋₁₀ aryl-C₁₋₃ alkylene.

In some embodiments, R^(a1), R^(c1) and R^(d1) are each H. In someembodiments, R^(a1) and R^(c1) are each H, and R^(d1) is C₁₋₆ alkyl. Insome embodiments, R^(a1) is selected from C₁₋₆ alkyl, C₂₋₆ alkenyl, C₃₋₇cycloalkyl, and C₆₋₁₀ aryl; R^(c1) is H, and R^(d1) is selected from Hand C₁₋₆ alkyl. In some embodiments, each R^(a1), R^(c1) and R^(d1) isindependently selected from H and C₁₋₆ alkyl.

In some embodiments, an azo compound of Formula (I) is azodicarbonamide(also known as AZDC, carbamoyliminourea, azo(bis)formamide, anddiazenedicarboxamide, CAS Registry No. 123-77-3) having the followingstructure:

or a salt thereof.

In some embodiments, an azo compound of Formula (I) is azodicarboxylicacid (CAS Registry No. 4910-62-7) having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (I) is diethyldiazenedicarboxylate (also known as DEAD, CAS Registry No. 1972-28-7)having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (I) is diisopropylazodicarboxylate (also known as DIAD, CAS Registry No. 2446-83-5) havingthe following structure:

or a salt thereof.

In some embodiments, the compound of Formula (I) is selected from anyone of the following compounds:

or a salt thereof.

In some embodiments, the composition contains from about 0.5 wt. % toabout 25 wt. %, from about 1 wt. % to about 20 wt. %, from about 1 wt. %to about 10 wt. %, from about 3 wt. % to about 5 wt. %, from about 2 wt.% to about 18 wt. %, or from about 3 wt. % to about 15 wt. % of the azocompound. In some embodiments, the aqueous composition contains about0.5 wt. %, about 1 wt. %, about 2 wt. %, about 3 wt. %, about 3.5 wt. %,about 4 wt. %, about 4.5 wt. %, about 5 wt. %, about 7.5 wt. %, about 10wt. %, about 15 wt. %, or about 20 wt. % of the azo compound.

In some embodiments, azo compound in the aqueous composition is thegas-generating chemical. That is, without being bound to any particulartheory, it is believed that upon activation, azo compound decomposes toproduce gas. Depending on the actual chemical structure of the azocompound, nitrogen gas, carbon monoxide, carbon dioxide, ammonia, loweralkyl amines, alkylene (for example, ethylene, propylene, or isobutene),or any combinations thereof, may be released upon decomposition of theazo compound.

For example, when the azo compound is azodicarbonamide (AZDC), the azocompound may decompose to produce a gaseous mixture is shown in Scheme1.

Referring to Scheme 1, when azodicarbonamide 1 is activated, forexample, by heat, the compound 1 decomposes to yield diimide 2 andisocyanic acid 3, as shown in equation (1). As shown in equation (2),the diimide 2 further disproportionates to produce nitrogen gas 4 andhydrogen gas 5. As shown in equation (3), in an aqueous environment,isocyanic acid 3 is hydrolyzed to produce ammonia gas 7 and carbondioxide 8. As shown in equation (4), the hydrogen gas that has beenproduced after disproportionation of diimide 2 may also reduce theunreacted azodicarbonamide 1, to produce hydrazinodicarboxamide 9, whichis no longer active and may not generate any gaseous compounds in thecomposition. Additionally, as shown in equation (5), azodicarbonamide 1may undergo a cyclization reaction to form urazole 10 and ammonia gas 7.Finally, as shown in equation (6), two moles of isocyanic acid 3 mayreact with one mole of the starting material azodicarbonamide 1 toproduce inactive hydrazinodicarboxamide 9, nitrogen gas 4, and alsocarbon monoxide 11. In sum, decomposition of azodicarbonamide (AZDC)yields nitrogen gas, hydrogen gas, ammonia gas, carbon dioxide gas, andcarbon monoxide gas, and also produces some amount of inactive compoundhydrazinodicarboxamide.

In another example, when the azo compound is azodicarboxylic acid, theazo compound may decompose to produce a gaseous mixture as shown inScheme 2.

Referring to scheme 2, azodicarboxylic acid 12 may decompose to producediimide 2 and carbon dioxide 8. (See equation 1). As shown in Scheme 1,the diimide 2 further disproportionates to produce nitrogen gas 4 andhydrogen gas 5. The hydrogen to gas 5, in turn, reduces the startingmaterial 12 to produce inactive hydrazinodicarboxamide 13 (as shown inequation 2), which can no longer decompose to produce gaseous compounds.

In yet another example, when the azo compound is diisopropylhydrazine-1,2-dicarboxylate, the azo compound may decompose to produce agaseous mixture as shown in Scheme 3.

Referring to scheme 3, diisopropyl hydrazine-1,2-dicarboxylate 14 maydecompose to produce diimide 2, carbon dioxide 8, and ethylene 15. (Seeequation 1). As shown in Scheme 1, the diimide 2 furtherdisproportionates to produce nitrogen gas 4 and hydrogen gas 5. Thehydrogen gas 5, in turn, reduces the starting material 14 to produceinactive diisopropyl hydrazine-1,2-dicarboxylate 16 (as shown inequation 2), which can no longer decompose to produce gaseous compounds.

In some embodiments, the decomposition of azo compound is activated byelevated temperature (for example, temperature in the wellbore greaterthan 100° C.), basic pH, presence of an activator compound (for example,any of the amine compounds described later), or any combination of theseactivating factors. In some embodiments, decomposition of azo compoundand gas release are activated by the presence of an organic amineactivator compound. In some embodiments, decomposition of azo compoundand gas release are activated by elevated temperature in the wellboreand the presence of an amine activator compound. In some embodiments,decomposition of azo compound and gas release are activated by basic pH,elevated temperature in the wellbore, and the presence of an organicamine compound.

In some embodiments, an azo compound decomposes at a temperature fromabout 80° C. to about 250° C., from about 100° C. to about 225° C., fromabout 120° C. to about 210° C., from about 125° C. to about 200° C., orfrom about 150° C. to about 200° C. In some embodiments, an azo compounddecomposes at about 100° C., about 120° C., about 125° C., about 140°C., about 150° C., about 175° C., about 180° C., about 200° C., about220° C., or about 250° C. In some embodiments, decomposition of the azocompound and release of gas is an endothermic process. In otherembodiments, decomposition of the azo compound and release of gas is anexothermic process.

In some embodiments, any one of compounds of Formula (I) upondecomposition generates a reduced dicarboxyl derivative of hydrazine ofFormula (V):

or salt thereof, where X¹ and X² are as described here for Formula (I).Examples of compounds of Formula (V) include hydrazine-1,2-dicarboxamide9 (Scheme 1), hydrazine-1,2-dicarboxylic acid 13 (Scheme 2), anddiisopropyl hydrazine-1,2-dicarboxylate 16 (Scheme 3).

In some embodiments, when an oxidizing compound is present in thewellbore fluid, the compound of Formula (V) reacts with the oxidizingcompound to produce the corresponding azo compound of Formula (I), forexample, as shown in Scheme 4.

Referring to scheme 4, an oxidizing compound in its oxidized statereacts with the dicarboxyl hydrazine compound to generate anitrogen-nitrogen double bond and hence to produce the azo compound offormula (I), and the reduced form of the oxidizing compound as abyproduct. That is, the compound of Formula (V) undergoes adehydrogenation reaction upon contact with the oxidizer compound toreproduce an azo compound of Formula (I). Examples of oxidizer aredescribed later.

Examples of Organic Amine Compounds

In some embodiments, an aqueous gas-generating composition of thepresent disclosure contains an organic amine compound.

In some embodiments, the organic amine compound is a primary, secondaryor tertiary amine of Formula (IVa):

or a salt thereof, where:

R^(n1), R^(n2) and R^(n3) are independently selected from H, C₁₋₆ alkyl,C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, 4-7 memberedheterocycloalkyl, and C₆₋₁₀ aryl, each of which is optionallysubstituted with 1, 2, or 3 substituents independently selected fromhydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆ alkyl)carbamyl, C₁₋₆alkylcarbonylamino, C₁₋₆ alkylsulfonylamino, aminosulfonyl, C₁₋₆alkylaminosulfonyl, di(C₁₋₆ alkyl)aminosulfonyl, aminosulfonylamino,C₁₋₆ alkylaminosulfonylamino, di(C₁₋₆ alkyl)aminosulfonylamino,aminocarbonylamino, C₁₋₆ alkylaminocarbonylamino, and di(C₁₋₆alkyl)aminocarbonylamino; or any two R^(n1) and R^(n2), or any twoR^(n2) and R^(n3), or any two R^(n1) and R^(n3) together with the N atomto which they are attached form a 4-7 membered heterocycloalkyl, whichis optionally substituted with 1, 2, 3, 4, or 5 substituentsindependently selected from C₁₋₆ alkyl, NH₂—C₁₋₆ alkylene, OH—C₁₋₆alkylene, hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆alkyl)amino, carboxy, carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆alkyl)carbamyl, C₁₋₆ alkylcarbonylamino, C₁₋₆ alkylsulfonylamino,aminosulfonyl, C₁₋₆ alkylaminosulfonyl, di(C₁₋₆ alkyl)aminosulfonyl,aminosulfonylamino, C₁₋₆ alkylaminosulfonylamino, di(C₁₋₆alkyl)aminosulfonylamino, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, and di(C₁₋₆ alkyl)aminocarbonylamino.

In some embodiments, R^(n1), R^(n2) and R^(n3) are independentlyselected from H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7 memberedheterocycloalkyl, each of which is optionally substituted with 1, 2, or3 substituents independently selected from hydroxyl, C₁₋₆ alkoxy, amino,C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and carbamyl.

In some embodiments, R^(n1) is H, and R^(n2) and R^(n3) areindependently selected from C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7membered heterocycloalkyl, each of which is optionally substituted with1, 2, or 3 substituents independently selected from hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.

In some embodiments, R^(n1), R^(n2) and R^(n3) are independentlyselected from H and Cu e alkyl, which is optionally substituted with 1,2, or 3 substituents independently selected from hydroxyl, C₁₋₆ alkoxy,amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, and carboxy.

In some embodiments, R^(n1), R^(n2) and R^(n3) are independently C₁₋₆alkyl, which is optionally substituted with 1, 2, or 3 substituentsindependently selected from hydroxyl, amino, and carboxy.

In some embodiments, any two R^(n1) and R^(n2), or any two R^(n2) andR^(n3), or any two R^(n1) and R^(n3) together with the N atom to whichthey are attached form a 4-7 membered heterocycloalkyl, which isoptionally substituted with 1, 2, 3, 4, or 5 substituents independentlyselected from C₁₋₆ alkyl, NH₂—C₁₋₆ alkylene, OH—C₁₋₆, alkylene,hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, and carbamyl.

In some embodiments, the compound of Formula (IVa) is triethanolamine(also known as tris(2-hydroxyethyl)amine, CAS Registry No. 102-71-6)having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (IVa) is selected from anyone of the following compounds:

or a salt thereof.

In some embodiments, the organic amine compound is ammonia (for example,aqueous ammonia solution), ammonium hydrochloride, ammonium sulfate,ammonium hydrosulfate, ammonium carbamate, ammonium acetate, or ammoniumoxalate.

In some embodiments, the organic amine compound is a hydrazine compoundof Formula (IVb):

or a salt thereof, where:

R^(n4), R^(n5), R^(n6), and R^(n7) are independently selected from H,C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, 4-7 memberedheterocycloalkyl, and C₆₋₁₀ aryl, each of which is optionallysubstituted with 1, 2, or 3 substituents independently selected fromhydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, carbamyl, C u e alkylcarbamyl, di(C₁₋₆ alkyl)carbamyl, C₁₋₆alkylcarbonylamino, C₁₋₆ alkylsulfonylamino, aminosulfonyl, C₁₋₆alkylaminosulfonyl, di(C₁₋₆ alkyl)aminosulfonyl, aminosulfonylamino,C₁₋₆ alkylaminosulfonylamino, di(C₁₋₆ alkyl)aminosulfonylamino,aminocarbonylamino, C₁₋₆ alkylaminocarbonylamino, and di(C₁₋₆alkyl)aminocarbonylamino; or

any two R^(n4) and R^(n5), or any two R^(n6) and R^(n7), together withthe N atom to which they are attached form a 4-7 memberedheterocycloalkyl, which is optionally substituted with 1, 2, 3, 4, or 5substituents independently selected from C₁₋₆ alkyl, hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, carbamyl,C₁₋₆ alkylcarbamyl, di(C₁₋₆ alkyl)carbamyl, C₁₋₆ alkylcarbonylamino,C₁₋₆ alkylsulfonylamino, aminosulfonyl, C₁₋₆ alkylaminosulfonyl, di(C₁₋₆alkyl)aminosulfonyl, aminosulfonylamino, C₁₋₆ alkylaminosulfonylamino,di(C₁₋₆ alkyl)aminosulfonylamino, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, and di(C₁₋₆ alkyl)aminocarbonylamino.

In some embodiments, R^(n4), R^(n5), R^(n6), and R^(n7) areindependently selected from H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7membered heterocycloalkyl, each of which is optionally substituted with1, 2, or 3 substituents independently selected from hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.

In some embodiments, R^(n4) and R^(n5) are each H, and R^(n6) and R^(n7)are independently selected from C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7membered heterocycloalkyl, each of which is optionally substituted with1, 2, or 3 substituents independently selected from hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.

In some embodiments, R^(n4), R^(n5) and R^(n6) are each H, and R^(n7) isselected from C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 6-12 membered aryl, eachof which is optionally substituted with 1, 2, or 3 substituentsindependently selected from C₁₋₆ alkyl, hydroxyl, C₁₋₆ alkoxy, amino,C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and carbamyl.

In some embodiments, R^(n4), R^(n5), R^(n6), and R^(n7) areindependently selected from H and C₁₋₆ alkyl, which is optionallysubstituted with 1, 2, or 3 substituents independently selected fromhydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, andcarboxy.

In some embodiments, R^(n4), R^(n5), R^(n6), and R^(n7) are eachindependently C₁₋₆ alkyl, which is optionally substituted with 1, 2, or3 substituents independently selected from hydroxyl, amino, and carboxy.

In some embodiments, any two R^(n4) and R^(n5), or any two R^(n6) andR^(n7), together with the N atom to which they are attached form a 4-7membered heterocycloalkyl, which is optionally substituted with 1, 2, 3,4, or 5 substituents independently selected from C₁₋₆ alkyl, hydroxyl,C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.

In some embodiments, a hydrazine compound of Formula (IVb) is selectedfrom hydrazine, hydrazine monohydrobromide, hydrazine hydrate, hydrazinesulfate, hydrazine acetate, hydrazine dihydrochloride, hydrazinemonohydrochloride, and hydrazine acetate.

In some embodiments, a hydrazine compound of Formula (IVb) is selectedfrom any one of the following compounds:

or salt thereof.

In some embodiments, the organic amine compound is an ethyleneiminecompound of Formula (IVc):

or a salt thereof, where:

n is an integer from 1 to 10,

R^(n8), R^(n9), R^(n10), and R^(n11) are independently selected from H,C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₃₋₇ cycloalkyl, 4-7 memberedheterocycloalkyl, and C₆₋₁₀ aryl, each of which is optionallysubstituted with 1, 2, or 3 substituents independently selected fromhydroxyl, C₁₋₆ alkoxy, NH₂—C₁₋₆ alkylene, OH—C₁₋₆ alkylene, amino, C₁₋₆alkylamino, di(C₁₋₆ alkyl)amino, carboxy, carbamyl, C₁₋₆ alkylcarbamyl,di(C₁₋₆ alkyl)carbamyl, C₁₋₆ alkylcarbonylamino, C₁₋₆alkylsulfonylamino, aminosulfonyl, C₁₋₆ alkylaminosulfonyl, di(C₁₋₆alkyl)aminosulfonyl, aminosulfonylamino, C₁₋₆ alkylaminosulfonylamino,di(C₁₋₆ alkyl)aminosulfonylamino, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, and di(C₁₋₆ alkyl)aminocarbonylamino; or

any two R^(n8) and R^(n9), or any two R^(n10) and R^(n11), together withthe N atom to which they are attached form a 4-7 memberedheterocycloalkyl, which is optionally substituted with 1, 2, 3, 4, or 5substituents independently selected from C₁₋₆ alkyl, NH₂—C₁₋₆ alkylene,OH—C₁₋₆ alkylene, hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆alkyl)amino, carboxy, carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆alkyl)carbamyl, C₁₋₆ alkylcarbonylamino, C₁₋₆ alkylsulfonylamino,aminosulfonyl, C₁₋₆ alkylaminosulfonyl, di(C₁₋₆ alkyl)aminosulfonyl,aminosulfonylamino, C₁₋₆ alkylaminosulfonylamino, di(C₁₋₆alkyl)aminosulfonylamino, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, and di(C₁₋₆ alkyl)aminocarbonylamino.

In some embodiments, R^(n8), R^(n9), R^(n10), and R^(n11) areindependently selected from H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7membered heterocycloalkyl, each of which is optionally substituted with1, 2, or 3 substituents independently selected from hydroxyl,C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.

In some embodiments, n is an integer from 1 to 8, and R^(n8), R^(n9),R^(n10) and R^(n11) are independently selected from H and C₁₋₆ alkyl,which is optionally substituted with 1, 2, or 3 substituentsindependently selected from amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, and carbamyl.

In some embodiments, n is an integer from 1 to 8, and R^(n8), R^(n9),R^(n10) and R^(n11) are each H. In some embodiments, R^(n8), R^(n9),R^(n10), and R^(n11) are each independently C₁₋₆ alkyl, which isoptionally substituted with 1, 2, or 3 substituents independentlyselected from amino and carboxy.

In some embodiments, any two R^(n8) and R^(n9), or any two R^(n10) andR^(n11), together with the N atom to which they are attached form a 4-7membered heterocycloalkyl, which is optionally substituted with 1, 2, 3,4, or 5 substituents independently selected from C₁₋₆ alkyl, NH₂—C₁₋₆alkylene, OH—C₁₋₆, alkylene, hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and carbamyl.

In some embodiments, the ethyleneimine compound of Formula (IVc) isselected from any one of the following compounds:

or a salt thereof.

In some embodiments, the gas-generating composition includes anycombination of EDA, DETA, TETA, TEPA, PEHA and HEHA. For example, thegas-generating composition includes TETA and TEPA (for example, in equalamounts by weight). In another example, the gas generating compositionincludes TEPA, DETA, and TETA (for example, in equal amounts by weight).

In some embodiments, the organic amine compound is ethyleneiminecompound selected from ethylene diamine (EDA), tetraethylene pentamine(TEPA), diethyletriamine (DETA), and polyethyleneimine, or a saltthereof.

In some embodiments, the organic amine compound is EDTA having thefollowing structure:

or a salt thereof.

In some embodiments, the organic amine compound is selected from any oneof the following compounds:

or a salt thereof.

In some embodiments, the organic amine compound is a polyethyleneimine,or a salt thereof. In some embodiments, the polyethyleneimine is linear.In other embodiments, the polyethyleneimine is branched (for example,CAS Reg. Nos. 9002-98-6, 25987-06-8). For example, a polyethyleneiminecan have from 2 to 100 termini (for example, 2 to 80, 2 to 75, 2 to 60,2 to 50, 2 to 40, 2 to 35, 2 to 25, 2 to 10, 2 to 5, 4 to 20, to 25, 10to 50, 25 to 75, 3 to 6, 5 to 15 termini). In some embodiments, apolyethyleneimine can have from 2 to 5, 4 to 6, 5 to 6, or 3 to 6termini. In some embodiments, branched polyethyleneimine is V-shaped orT-shaped, depending on the method by which polyethyleneimine has beensynthesized. In some embodiments, the polyethyleneimine has both linearand branched fragments. In some embodiments, the polyethyleneimine isalkylated (for example, methylated or ethylated). In some embodiments,the polyethyleneimine is PEGylated (for example reacted with ethyleneoxide to form polyethylene glycol (PEG) chains having molecular weightbetween about 1.000 Da and about 100,000 Da).

In some embodiments, polyethyleneimine has average molecular weightbetween about 0.1 kDa to about 500 kDa. For example, molecular weight ofpolyethyleneimine may be between about 500 Da and about 100,000 Da.Polyethyleneimine described here can have a molecular weight of about100,000 Da, 95,000 Da, 90,000 Da, 85,000 Da, 80.000 Da, 75,000 Da,70,000 Da, 65,000 Da, 60,000 Da, 55,000 Da, 50,000 Da, 45,000 Da, 40,000Da, 35,000 Da, 30,000 Da, 25,000 Da, 20,000 Da, 15,000 Da, 10,000 Da,9.000 Da, 8,000 Da, 7,000 Da, 6,000 Da, 5,000 Da, 4,000 Da, 3,000 Da,2,000 Da, 1,000 Da, 900 Da, 800 Da, 700 Da, 600 Da, or 500 Da. In someembodiments, the molecular weight of polyethyleneimine is between about500 Da and about 50,000 Da. In some embodiments, molecular weight ofpolyethyleneimine is between about 500 Da and about 40,000 Da. In someembodiments, molecular weight of polyethyleneimine is between about1,000 Da and about 40,000 Da. In some embodiments, molecular weight ofthe polyethyleneimine is between about 5,000 Da and about 40,000 Da. Insome embodiments, molecular weight of polyethyleneimine is between about10,000 Da and about 40,000 Da.

In some embodiments, the organic amine is a hydrazide compound havingFormula (IIa) or Formula (IIb):

or a salt thereof, where:

R¹ is selected from H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₃₋₇ cycloalkyl, C₆₋₁₀aryl, and —NH—NH₂, where said C₆₋₁₀ aryl is optionally substituted with1, 2, or 3 substituents independently selected from C₁₋₆ alkyl,hydroxyl, amino, C₁₋₆ alkoxy, and NO₂; and

R² is selected from H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₃₋₇ cycloalkyl, C₆₋₁₀aryl, carboxy, carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl,aminosulfonyl, C₁₋₆ alkylaminosulfonyl, and di(C₁₋₆ alkyl)aminosulfonyl.

In some embodiments, R¹ is selected from H, C₁₋₆ alkyl, C₆₋₁₀ aryl, and—NH—NH₂, where said C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3substituents independently selected from C₁₋₆ alkyl, hydroxyl, amino,C₁₋₆ alkoxy, and NO₂. In some embodiments, R¹ is H. In some embodiments,R¹ is —NH—NH₂. In some embodiments, R¹ is phenyl. In some embodiments,R¹ is selected from C₁₋₆ alkyl and C₆₋₁₀ aryl, where said C₆₋₁₀ aryl isoptionally substituted with 1, 2, or 3 substituents independentlyselected from C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂. In someembodiments, R¹ is C₁₋₆ alkyl. In some embodiments, R¹ is selected fromC₁₋₆ alkyl and C₆₋₁₀ aryl, where said C₆₋₁₀ aryl is optionallysubstituted with 1, 2, or 3 substituents independently selected fromC₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂. In some embodiments,R¹ is C₆₋₁₀ aryl, which is optionally substituted with 1, 2, or 3independently selected C₁₋₆ alkyl groups. In some embodiments, R¹ isselected from C₆₋₁₀ aryl and —NH—NH₂, where said C₆₋₁₀ aryl isoptionally substituted with 1, 2, or 3 substituents independentlyselected from C₁₋₆ alkyl and NO₂.

R² is selected from H, C₁₋₆ alkyl, carboxy, carbamyl, C₁₋₆alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl, aminosulfonyl, C₁₋₆alkylaminosulfonyl, and di(C₁₋₆ alkyl)aminosulfonyl. In someembodiments, R² is H. In some embodiments, R² is selected from carboxy,carbamyl, and aminosulfonyl. In some embodiments, R² is selected from H,carboxy, carbamyl, and aminosulfonyl. In some embodiments, R² isselected from C₁₋₆ alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl, C₁₋₆alkylaminosulfonyl, and di(C₁₋₆ alkyl)aminosulfonyl. In someembodiments, R² is carboxy. In some embodiments, R² is carbamyl. In someembodiments, R² is aminosulfonyl. In some embodiments, R² is selectedfrom H, carboxy, carbamyl, and aminosulfonyl.

In some embodiments, R¹ is selected from C₁₋₆ alkyl and C₆₋₁₀ aryl,where said C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3substituents independently selected from C₁₋₆ alkyl, hydroxyl, amino,C₁₋₆ alkoxy, and NO₂; and R² is selected from H, carboxy, carbamyl, andaminosulfonyl.

In some embodiments, R¹ is C₁₋₆ alkyl and R² is H. In some embodiments,R¹ is C₆₋₁₀ aryl, which is optionally substituted with 1, 2, or 3substituents independently selected C₁₋₆ alkyl groups; and R² is H.

In some embodiments, the compound of Formula (IIa) is a carbohydrazide(also known as 1,3-diaminourea, CAS Registry No. 497-18-7) having thefollowing structure:

or a salt thereof.

In some embodiments, the compound of Formula (IIa) is selected from anyone of the following compounds:

or a salt thereof.

In some embodiments, the compound of Formula (IIb) is ap-toluenesulfonyl hydrazide (also known as tosylhydrazide, CAS RegistryNo. 1576-35-8) having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (IIb) is selected from anyone of the following compounds:

or a salt thereof.

In some embodiments, the hydrazide compound is selected fromcarbohydrazide and p-toluenesulfonyl hydrazide, or a salt thereof.

In some embodiments, the organic amine is a semicarbazide compoundhaving Formula (III):

or a salt thereof, where:

R³ is selected from H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₃₋₇ cycloalkyl, andC₆₋₁₀ aryl; and

R⁴ is selected from H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₃₋₇ cycloalkyl, C₆₋₁₀aryl, carboxy, carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl,aminosulfonyl, C₁₋₆ alkylaminosulfonyl, di(C₁₋₆ alkyl)aminosulfonyl,C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀ aryl, S(═O)₂C₁₋₆ alkyl, and S(═O)₂C₆₋₁₀aryl;

where said C₆₋₁₀ aryl in R³ or R⁴ is optionally substituted with 1, 2,or 3 substituents independently selected from C₁₋₆ alkyl, hydroxyl,amino, C₁₋₆ alkoxy, and NO₂.

In some embodiments, R³ is selected from H, C₁₋₆ alkyl, and C₆₋₁₀ aryl.In some embodiments, R³ is H. In some embodiments, R³ is C₁₋₆ alkyl. Insome embodiments, R³ is C₆₋₁₀ aryl optionally substituted with 1, 2, or3 substituents selected from C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy,and NO₂.

In some embodiments, R⁴ is selected from H, C₁₋₆ alkyl, C₆₋₁₀ aryl,carboxy, carbamyl, C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀ aryl, S(═O)₂C₁₋₆ alkyl,and S(═O)₂C₆₋₁₀ aryl; where said C₆₋₁₀ aryl is optionally substitutedwith 1, 2, or 3 substituents independently selected from C₁₋₆ alkyl,hydroxyl, amino, C₁₋₆ alkoxy, and NO₂. In some embodiments, R⁴ isselected from H and C₁₋₆ alkyl. In some embodiments, R⁴ is selected fromC₁₋₆ alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl, aminosulfonyl, C₁₋₆alkylaminosulfonyl, and di(C₁₋₆ alkylaminosulfonyl. In some embodiments,R⁴ is selected from carboxy, carbamyl, C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀ aryl,S(═O)₂C₁₋₆ alkyl, and S(═O)₂C₆₋₁₀ aryl; where said C₆₋₁₀ aryl isoptionally substituted with 1, 2, or 3 substituents independentlyselected from C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂. In someembodiments, R⁴ is selected from carboxy and carbamyl. In someembodiments, R⁴ is selected from C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀ aryl,S(═O)₂C₁₋₆ alkyl, and S(═O)₂C₆₋₁₀ aryl; where said C₆₋₁₀ aryl isoptionally substituted with 1, 2, or 3 substituents independentlyselected from C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂. In someembodiments, R⁴ is selected from C(═O)C₆₋₁₀ aryl and S(═O)₂C₆₋₁₀ aryl;where said C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3substituents independently selected from C₁₋₆ alkyl, hydroxyl, amino,C₁₋₆ alkoxy, and NO₂. In some embodiments, R⁴ is H. In some embodiments,R⁴ is C(═O)C₁₋₆ alkyl. In some embodiments, R⁴ is C(═O)C₆₋₁₀ aryl, wheresaid C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3 substituentsindependently selected from C₁₋₆ alkyl, hydroxyl, and NO₂. In someembodiments, R⁴ is S(═O)₂C₁₋₆ alkyl. In some embodiments, R⁴ isS(═O)₂C₆₋₁₀ aryl, where said C₆₋₁₀ aryl is optionally substituted with1, 2, or 3 substituents independently selected from C₁₋₆ alkyl,hydroxyl, and NO₂. In some embodiments, R⁴ is S(═O)₂C₆₋₁₀ aryl, wheresaid C₆₋₁₀ aryl is optionally substituted with 1, 2, or 3 independentlyselected C₁₋₆ alkyl groups.

In some embodiments, R³ is selected from H, C₁₋₆ alkyl, and C₆₋₁₀ aryl,and R⁴ is selected from H, C₁₋₆ alkyl, carboxy, carbamyl, C(═O)C₁₋₆alkyl, C(═O)C₆₋₁₀ aryl, S(═O)₂C₁₋₆ alkyl, and S(═O)₂C₆₋₁₀ aryl.

In some embodiments, R³ is selected from H, C₁₋₆ alkyl, and C₆₋₁₀ aryl,and R⁴ is selected from carboxy, carbamyl, C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀aryl, S(═O)₂C₁₋₆ alkyl, and S(═O)₂C₆₋₁₀ aryl; where said C₆₋₁₀ aryl isoptionally substituted with 1, 2, or 3 substituents independentlyselected from C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂.

In some embodiments, R³ is selected from H, C₁₋₆ alkyl, and C₆₋₁₀ aryl,and R⁴ is selected from C(═O)C₁₋₆ alkyl, C(═O)C₆₋₁₀ aryl, S(═O)₂C₁₋₆alkyl, and S(═O)₂C₆₋₁₀ aryl; where said C₆₋₁₀ aryl is optionallysubstituted with 1, 2, or 3 substituents independently selected fromC₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂.

In some embodiments, R³ is selected from H and C₁₋₆ alkyl, and R⁴ isS(═O)₂C₆₋₁₀ aryl, where said C₆₋₁₀ aryl is optionally substituted with1, 2, or 3 independently selected C₁₋₆ alkyl groups.

In some embodiments, the compound of Formula (III) is ahydrazinecarboxamide (also known as aminourea or semicarbazide CASRegistry No. 57-56-7) having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (III) is ap-toluenesulfonyl semicarbazide (also known as tosylsemicarbazide, CASRegistry No. 10396-10-8) having the following structure:

or a salt thereof.

In some embodiments, the compound of Formula (III) is selected from anyone of the following compounds:

or a salt thereof.

An organic amine compound in the gas-generating composition of thepresent disclosure may catalyze the gas-generating decompositionreaction of the azo compound. Without being bound to any particulartheory, it is believed that an amine compound non-covalently binds to acarbonyl group of the azo compound, and thereby decreases the activationenergy of the radical decomposition reaction of the azo compound. Thatis, an amine compound serves as a catalyst and induces decomposition ofthe azo compound and production of the diimide compound, which, it turn,further decomposes to yield nitrogen gas and hydrogen gas. Examples ofnon-covalent interactions of amine compounds and azo compounds includehydrogen bonds, Van-der-Waals forces, electrostatic attractions, andhydrophobic interactions. In some embodiments, an amine compound alsocatalyzes the decomposition reaction of the diimide compound andsubsequent N₂ and H₂ gas generation. In some embodiments, addition of anamine compound to the azo compound-containing composition decreases thedecomposition temperature of the azo compound by a factor of 0.5 interms of Celsius. That is, if an azo compound decomposes to produce gasat about 200° C. in the absence of an amine, then in the presence of theamine the azo compound decomposes at about 100° C. In some embodiments,addition of an organic amine decreases the decomposition temperature ofthe azo compound by a factor of about 0.6 in terms of Celsius, about 0.7in terms of Celsius, about 0.8 in terms of Celsius, about 0.9 in termsof Celsius, or about 0.95 in terms of Celsius.

Typically, an organic amine compound is present in the aqueouscomposition in 1:1 molar ratio with the azo compound. In someembodiments, an organic amine compound is present in the gas-generatingcomposition in molar excess with respect to the azo compound. Forexample, the organic amine compound may be present in about 10:1, about8:1, about 5:1, about 3:1, about 2:1, or about 3:2 molar excess withrespect to the azo compound. In some embodiments, the compositioncontains from about 0.5 wt. % to about 25 wt. %, from about 1 wt. % toabout 20 wt. %, from about 1 wt. % to about 10 wt. %, from about 1 wt. %to about 5 wt. %, from about 3 wt. % to about 5 wt. %, from about 2 wt.% to about 18 wt. %, or from about 3 wt. % to about 15 wt. % of theamine compound based on the weight of the composition. In someembodiments, the aqueous composition contains about 0.5 wt. %, about 1wt. %, about 2 wt. %, about 3 wt. %, about 3.5 wt. %, about 4 wt. %,about 4.5 wt. %, about 5 wt. %, about 7.5 wt. %, about 10 wt. %, about15 wt. %, or about 20 wt. % of the organic amine compound based on theweight of the aqueous composition.

Examples of Oxidizing Compounds

In some embodiments, an aqueous gas-generating composition of thepresent disclosure may be admixed with an oxidizing compound. In someembodiments, the oxidizing compound is inorganic. Suitable examples ofinorganic oxidizes include hydrogen peroxide, sodium hypochlorite,calcium hypochlorite, peroxysulfate, peroxycarbonate, peroxyborate, andperoxides of alkali and alkaline earth metals (for example, sodiumperoxide, potassium peroxide, or calcium peroxide). In some embodiments,the oxidizing compound is organic, for example, water soluble or waterdispersible peracids, peroxides and hydroperoxides (for example,peracetic acid, benzoyl peroxide and t-butyl hydrogen peroxide).

In some embodiments, oxidizing compound is selected from aperoxysulfate, a peroxycarbonate, or a peroxyborate of alkali andalkaline earth metals, a peroxide (for example, alkali metal peroxide,alkali earth metal peroxide, benzoyl peroxide or t-butyl hydrogenperoxide), a hypochlorite (for example, sodium hypochlorite or calciumhypochlorite), and an organic peracid (for example, peracetic acid).

Typically, an oxidizing compound is present in a wellbore fluid in about1:1 molar ratio with the azo compound. In some embodiments, an oxidizingcompound is present in the wellbore fluid in molar excess with respectto the azo compound. For example, the oxidizer compound may be presentin about 10:1, about 8:1, about 5:1, about 3:1, about 2:1, or about1.5:1 molar excess with respect to the azo compound. In otherembodiments, the azo compound is present in molar excess with respect tothe oxidizer, for example, azo compound is present in a wellbore fluidin about 10:1, about 8:1, about 5:1, about 3:1, about 2:1, or about1.5:1 molar excess with respect to the oxidizer.

In some embodiments, addition of the oxidizer compound to a wellborefluid increases the amount of gaseous compounds produced upon activationof the gas-generating compound, for example, by converting the inactivereduced form of the gas-generating compound to the active form. Anexample of this process as applied to the azo compounds is shown inScheme 4.

Examples of Combinations of Ingredients and Properties of theCompositions

In some embodiments, a gas-generating aqueous composition contains anazo compound in an amount from about 1 wt. % to about 10 wt. %, and anorganic amine in an amount from about 1 wt. % to about 10 wt. % based onthe weight of the composition.

In some embodiments, a gas-generating aqueous composition containsazodicarbonamide in an amount from about 1 wt. % to about 10 wt. %, andcarbohydrazide in an amount from about 1 wt. % to about 10 wt. %.

In some embodiments, a gas-generating aqueous composition containsazodicarbonamide in an amount from about 1 wt. % to about 10 wt. %, andp-toluenesulfonyl semicarbazide in an amount from about 1 wt. % to about10 wt. %.

In some embodiments, a gas-generating aqueous composition containsazodicarbonamide in an amount from about 1 wt. % to about 10 wt. %, andethylene diamine in an amount from about 1 wt. % to about 10 wt. %.

In some embodiments, a gas-generating aqueous composition containsazodicarbonamide in an amount from about 1 wt. % to about 10 wt. %, andtriethanolamine in an amount from about 1 wt. % to about 10 wt. %.

In some embodiments, a gas-generating aqueous composition containsazodicarbonamide in an amount from about 1 wt. % to about 10 wt. %, andtetraethylene pentamine (TEPA) in an amount from about 1 wt. % to about10 wt. %.

In any of the aforementioned embodiments, azodicarbonamide may bepresent in an amount from about 3 wt. % to about 5 wt. %, and any of theorganic amines may be present in an amount forma bout 1 wt. % to about 5wt. %.

In some aspects of the aforementioned embodiments, the compositioncontains a viscosifier in an amount from about 0.1 wt. % to about 1 wt.% based on the weight of the composition (for example, about 0.5 wt. %or about 0.8 wt. %). In these aspects, the viscosifier may be xanthan,diutan or vinylphosphonate-grafted hydroxy cellulose (HEC).

In some aspects of the aforementioned embodiments, the compositioncontains a foaming surfactant or a foam-stabilizing surfactant in anamount from about 1 wt. % to about 5 wt. % based on the weight of theaqueous composition (for example, sodium lauryl sulfate and/orhydroxysultaine surfactants).

In yet other aspects of the aforementioned embodiments, pH compositionof the composition is less than about 9, less than about 8, less thanabout 7, less than about 6, less than about 5, less than about 4, lessthan about 3, less than about 2, or less than about 1. For example, pHof the aqueous composition is from about 1 to about 9, from about 2 toabout 9, from about 3 to about 9, from about 4 to about 9, from about 5to about 9, from about 6 to about 8, or from about 6 to about 7.

Examples of Viscosifiers

In some embodiments, an aqueous gas-generating composition of thepresent disclosure contains a viscosifier. In some embodiments, aviscosifier is a clay, a surfactant, a synthetic polymer, or abiopolymer. In some embodiments, the viscosifier is a bentonite,laponite, attapulgite, sepiolite, phyllosilicate, silica, or anorganophilic clay. In some embodiments, the viscosifier is awater-soluble polyacrylate, a polyurethane, a polyether, apolymethacrylate, an acrylamide based polymer, sulfonated polystyrene(SPS), polyamine, polyamide, polyglycol, polyvinylacetate orpolydiallyldimethylammonium chloride (polyDADMAC). In some embodiments,the viscosifier is a biobased polymer selected from starch, crosslinkedstarch, or cellulose (including its derivatives). In some embodiments,the viscosifier is an alkylated cellulose or a hydroxyalkylatedcellulose, for example, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, or vinylphosphonate graftedhydroxyethylcellulose (HEC). The viscosifier can include a substitutedor unsubstituted polysaccharide selected from diutan, xanthan, andxylinan. In some embodiments, the viscosifier is diutan. In someembodiments, the viscosifier is xanthan. In some embodiments, thepolymer is a vinyl phosphonated hydroxyethyl cellulose.

Viscosifier gives the aqueous gas-generating composition its basicrheological properties, modulates the viscosity of the composition andprovides shear-rate (for example, low shear rate) viscosity andweight-material suspension. In addition, some of the gas-generatingcompounds described here (for example, azo compounds) are sparinglywater-soluble, and precipitate quickly after mixing with water. Additionof the viscosifier to the composition suspends the gas-generatingcompound in water and allows to store the composition for prolongedperiods of time without settling.

In some embodiments, the composition contains from about 0.1 wt. % toabout 10 wt. %, from about 0.2 wt. % to about 9 wt. %, from about 0.3wt. % to about 8 wt. %, from about 0.5 wt. % to about 5 wt. %, or fromabout 0.1 wt. % to about 1 wt. % of the viscosifier based on the weightthe aqueous composition. In some embodiments, the aqueous compositioncontains about 0.1 wt. %, about 0.2 wt. %, about 0.3 wt. %, about 0.5wt. %, about 0.6 wt. %, about 0.8 wt. %, about 1 wt. %, about 1.5 wt. %,about 2 wt. %, about 2.5 wt. %, about 3 wt. %, about 3.5 wt. %, or about5 wt. % of the viscosifier.

In some embodiments, viscosity of the aqueous composition is from about1 cP to about 1000 cP, from about 5 cP to about 500 cP, from about 10 cPto about 300 cP, or from about 20 cP to about 200 cP. In someembodiments, viscosity of the composition is from about 5 cP to about500 cP.

In some embodiments, the aqueous composition is a clear solution. Insome embodiments, the aqueous composition is a suspension. In theseembodiments, the suspension may contain particles of a solid material,for example, azodicarbonamide, with an average diameter from about 10 nmto about 100 μm, or from about 1 μm to about 10 μm (for example, about 1μm, about 2 μm, about 3 μm, about 5 μm, or about 10 μm). In someembodiments, the solid material in the suspension does not settle(precipitate) for a prolonged period of time (for example, about 1 hour,about 5 hours, about 12 hours, about 24 hours, about 48 hours, about 2days, about 5 days, or about 1 week or longer).

Examples of Foaming or Foam Stabilizing Surfactants

In some embodiments, an aqueous gas-generating composition of thepresent disclosure includes a water soluble foaming surfactant. As usedhere, the term “foaming surfactant” includes foam stabilizingsurfactants that are soluble in water.

In some embodiments, foaming surfactant is negatively charged (forexample, anionic surfactant). In other embodiments, foaming surfactantis positively charged (for example, cationic surfactant). In someembodiments, foaming surfactant is neutral. In some aspects of theseembodiments, foaming surfactant is zwitterionic (having a positive and anegative electrical charge so that the net charge of the entire moleculeof the surfactant is zero). Suitable foaming surfactants includepolymeric surfactants, block copolymer surfactants, di-block polymersurfactants, hydrophobically modified hydrophilic polymer surfactants,fluoro-surfactants, and surfactants containing a non-ionic spacer-armcentral extension and an ionic or nonionic polar group. In someexamples, the non-ionic spacer-arm central extension can be the resultof at least one of polypropoxylation and polyethoxylation (PEGylation).

Suitable examples of non-ionic surfactants include polyoxyethylene alkylethers, polyoxyethylene alkylphenol ethers, polyoxyethylene laurylethers, polyoxyethylene sorbitan monooleates, polyoxyethylene alkylesters, polyoxyethylene sorbitan alkyl esters, ethoxylatedtrimethylnonanols, and polyoxyalkylene glycol modified polysiloxanesurfactants. Other suitable examples of non-ionic surfactants includePEGylated long chain fatty alcohols or fatty acids, for example, aC₁₂₋₁₆ alcohol, PEGylated alkyl amine or an amide, co-polymerizationproducts of ethylene oxide and propylene oxide, fatty esters ofglycerol, sucrose, or sorbitol, alkylated fatty acid amides, fatty amineoxides, polyoxyalkylene alkyl ethers like polyethylene glycol long chainalkyl ether, polyoxyalkylene sorbitan ethers, polyoxyalkylene alkoxylateesters, polyoxyalkylene alkylphenol ethers, alkylated polysaccharides,and polyvinylmethylether. In certain embodiments, the non-ionicsurfactant is a polyoxyethylene fatty alcohol or mixture ofpolyoxyethylene fatty alcohols.

Suitable examples of anionic surfactants include C₈₋₃₀ alkyl sulfates(for example, lauryl sulfate), C₁₀₋₃₀ alkyl acrylates,alkylbenzenesulfonic acids (for example, hexylbenzenesulfonic acid,octylbenzenesulfonic acid, decylbenzenesulfonic acid,dodecylbenzenesulfonic acid, cetylbenzenesulfonic acid ormyristylbenzene sulfonic acid), sulfate esters of monoalkylpolyoxyethylene ethers, alkylnapthylsulfonic acid; sodium lauryl sulfateand its salts, sulfonated glyceryl esters of fatty acids like sulfonatedmonoglycerides of coconut oil acids, sodium octahydroanthracenesulfonate. For any of the anionic surfactant described here, thecounterion can be any suitable counterion, for example, H⁺, Na⁺, K⁺,Li⁺, Zn²⁺, NH⁴⁺, Ca²⁺, Mg²⁺, Zn²⁺, or Al³⁺.

Suitable cationic surfactants can include at least one of an argininemethyl ester, an alkanolamine, an alkylenediamide, an amine oxide, analkylamine oxide, an ethoxylated amide, an ethoxylated fatty amine, anethoxylated alkyl amine, an alkyl betaine, an alkylamidobetaine, and asurfactant containing a quaternary ammonium group. Suitable examples ofcationic surfactants include quaternary ammonium hydroxides (forexample, octyl trimethyl ammonium hydroxide, dodecyl trimethyl ammoniumhydroxide, hexadecyl trimethyl ammonium hydroxide, octyl dimethyl benzylammonium hydroxide, decyl dimethyl benzyl ammonium hydroxide, didodecyldimethyl ammonium hydroxide, dioctadecyl dimethyl ammonium hydroxide,tallow trimethyl ammonium hydroxide or coco trimethyl ammoniumhydroxide), fatty amines, fatty acid amides, basic pyridinium compounds,and quaternary ammonium bases of benzimidazolines, polyethoxylatedamines, and polypropoxylated amines.

Some examples of foaming surfactants include sorbitan monooleate,polyglycol-modified trimethsilylated silicate, cetyltrimethylammoniumchloride, an ethoxylated nonyl phenol phosphate ester, a C₁₂₋₂₂ alkylphosphonate, a sulfonate methyl ester, a hydrolyzed keratin, apolyoxyethylene sorbitan monopalmitate, a polyoxyethylene sorbitanmonostearate, a polyoxyethylene sorbitan monooleate, a linear alcoholalkoxylate, an alkyl ether sulfate, a linear nonyl-phenol, polyethyleneglycol, an ethoxylated castor oil, dipalmitoyl-phosphatidylcholine,sodium 4-(heptylnonyl)benzenesulfonate, polyoxyethylene nonyl phenylether, sodium dioctyl sulfosuccinate, tetraethyleneglycoldodecylether,sodium octylbenzenesulfonate, sodium hexadecyl sulfate, sodium laurethsulfate, decylamine oxide, dodecyl betaine, dodecylamine oxide,N,N,N-trimethyl-1-octadecaammonium chloride, xylene sulfonate, sodiumdodecyl sulfate, cetyltrimethylammonium bromide, cocoamidopropylbetaine, cocoamidopropyl dimethylamine oxide.

Examples of foaming surfactants also include C₅₋₅₀ hydrocarbylsulfates,C₅₋₅₀ hydrocarbylsulfate C₁₋₂₀ hydrocarbyl esters, where the C₁₋₂₀hydrocarbyl is C₁₋₂₀ alkyl or C₂₋₂₀ alkenyl, C₅₋₂₀ alkylsulfate, a C₅₋₂₀alkylsulfate C₁₋₂₀ alkyl esters, and C₅₋₂₀ alkylbisulfates.

In some embodiments, the foaming surfactant is a C₁₋₁₀ hydrocarbylamidoC₁₋₅ alkylbetaine (for example, lauramidopropyl betaine). In someembodiments, the foaming surfactant is a C₁₋₁₀ hydrocarbylamido C₁₋₅alkyldimethylamine oxide (for example, lauramidopropyl dimethylamineoxide).

In some embodiments, the foaming surfactant contains a hydroxysulfobetaine group (also known as hydroxysultaine group). In someembodiments, the foaming surfactant is C₅₋₂₅ alkyl or C₅₋₂₅ alkenylamidopropyl hydroxysultaine (for example, lauramidopropylhydroxysultaine, cocamidopropyl hydroxysultaine, oleamidopropylhydroxysultaine, tallowamidopropyl hydroxysultaine, or erucamidopropylhydroxysultaine). In some embodiments, the foaming surfactant is C₈₋₁₆alkyl hydroxy sulfobetaine or C₈₋₁₆ alkenyl hydroxy sulfobetaine.Suitable examples of these surfactants include didodecylmethyl hydroxylsulfobetaine, lauryl hydroxysultaine, and octadecyl hydroxysulfobetaine.

In some embodiment, the foaming surfactant is advantageously insensitiveto the storing conditions of the gas-generating fluid and does not loseits properties due to the presence of salts in the fluid and totemperature of the fluid. In some embodiments, the foaming surfactant isresistant to degradation by oxidizing agents like sodium hypochlorite.

Foaming surfactant facilitates formation of foam (increase in volume) inthe composition when the gas-generating compound is activated andproduces gas (for example, N₂). A foaming surfactant reduces surfacetension of water in the composition and promotes formation of the foambubbles filled with the gas that is being generated. Without being boundto a particular theory, it is believed that formation of foam bubblesenhances variable density and compressibility of the fluid to which agas-generating composition of the present disclosure is added and inwhich the gas is generated.

In some embodiments, the aqueous composition contains from about 1 wt. %to about 50 wt. %, from about 1 wt. % to about 40 wt. %, from about 1wt. % to about 30 wt. %, from about 1 wt. % to about 25 wt. %, fromabout 1 wt. % to about 20 wt. %, from about 1 wt. % to about 15 wt. %,from about 2 wt. % to about 20 wt. %, from about 3 wt. % to about 20 wt.%, from about 4 wt. % to about 15 wt. %, or from about 5 wt. % to about15 wt. % based on the weight of the aqueous composition. In someembodiments, the aqueous composition contains about 1 wt. %, about 2 wt.%, about 3 wt. %, about 4 wt. %, about 5 wt. %, about 10 wt. %, or about15 wt. %.

In some embodiments, density of the composition is in the range of about70 pounds per cubic foot (pcf) to about 150 pcf, about 20 pcf to about250 pcf, or about 50 pcf to about 150 pcf. For example, the density ofthe composition is about 20 pcf, about pcf, about 40 pcf, about 50 pcf,about 70 pcf, about 85 pcf, about 100 pcf, about 120 pcf, about 150 pcf,or about 200 pcf.

Examples of Additional Ingredients

In some embodiments, an aqueous gas-generating composition of thepresent application also contains at least one additional component. Itis understood by one skilled in the art that an additive may beclassified under more than one category. For example, sodium hydrogenphosphate may be considered as salt of a weak acid, namely phosphoricacid and a strong base, namely sodium hydroxide. It is also a buffer,because it has both acid and base components that can function as abuffering agent. The same compound can also function as a calciumprecipitating agent, since calcium phosphate that is formed in thereaction between calcium hydroxide or calcium silicate, both of whichare components of set cement and sodium hydrogen phosphate, is insolublein water. Similarly, citric acid and an organic base (for example,ethanolamine), or an inorganic base (for example, sodium hydroxide orsodium phosphate) forms a buffer system that contains partiallyneutralized citric acid. The resulting citrate salt is a calciumchelating agent as well as calcium precipitating agent while functioningas a component of the buffer system.

In some embodiments, the aqueous composition includes an inorganic salt.The salt can be about 1% to about 10% by weight of the composition. Thesalt can be selected from NaCl, NaBr, KCl, KBr, NaHCO₃, Na₂CO₃, CaCl₂,MgCl₂, NaNO₃, KNO₃, NaC₂H₃O₂, KC₂H₃O₂, NaCHO₂, KCHO₂, or anycombinations thereof. For example, the salt can be selected from thegroup consisting of NaCl, KCl, and combinations thereof.

The aqueous composition may include a formate salt. Suitable examples offormates include at least one alkali metal formate like sodium formateor potassium formate. Other suitable formates may also be included. Insome embodiments, the aqueous composition contains at least twoformates. An amount of the formate or a combination of the formates inthe aqueous composition may range from about 1 wt. % to about 20 wt. %,about 5 wt. % to about 15 wt. %, or about 10 wt. % to about 15 wt. %.For example, the slurry may contain about 1 wt. %, about 10 wt. %, about15 wt. %, or about 20 wt. % of a formate or combination of formates.

An amount of an optional additional component in the composition, forexample, an inorganic salt, a formate salt, a buffering agent or achelating agent, an ultra-fine particulate inorganic material or anycombination thereof, may vary from about 0.1 wt. % to about 30 wt. %, orfrom about 0.5 wt. % to about 20 wt. % based on the weight of theaqueous composition. The composition may also include an ash, forexample, a soda ash, and a bicarbonate, for example, sodium bicarbonate.

Salts of Acidic and Basic Compounds

In some embodiments, a salt of a compound of any one of the formulasdisclosed here (for example, azo compound, hydrazide compound,semicarbazide compound, amine compound, hydrazine compound,ethyleneimine derived compounds, or a polyethyleneimine) is formedbetween an acid and a basic group of the compound, for example, an aminofunctional group, or a base and an acidic group of the compound, forexample, a carboxyl functional group. According to another embodiment,the salt of the compound is an acid addition salt, or a base additionsalt.

In some embodiments, acids commonly employed to form salts of thecompounds of any one of the formulas disclosed here include inorganicacids, for example, hydrochloric acid, sulfuric acid and phosphoricacid. Alternatively or in addition, the acids include organic acids, forexample, p-toluenesulfonic acid, salicylic acid, tartaric acid,bitartaric acid, ascorbic acid, maleic acid, fumaric acid, gluconicacid, glucuronic acid, formic acid, glutamic acid, methanesulfonic acid,ethanesulfonic acid, benzenesulfonic acid, lactic acid, oxalic acid,para-bromophenylsulfonic acid, carbonic acid, succinic acid, citricacid, benzoic acid and acetic acid, as well as related inorganic andorganic acids. Such salts can include sulfate, pyrosulfate, bisulfate,sulfite, bisulfite, phosphate, monohydrogenphosphate,dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide,iodide, acetate, propionate, decanoate, caprylate, formate, isobutyrate,caprate, heptanoate, propiolate, oxalate, malonate, succinate, suberate,sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate,benzoate, chlorobenzoate, methylbenzoate, hydroxybenzoate,methoxybenzoate, phthalate, terephthalate, sulfonate, xylene sulfonate,phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate,β-hydroxybutyrate, glycolate, maleate, tartrate, methanesulfonate,propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate,mandelate and other salts. In one embodiment, acid addition saltsinclude those formed with mineral acids, for example, hydrochloric acidand sulfuric acid, and those formed with organic acids, for example,acetic acid.

In some embodiments, bases commonly employed to form salts of thecompounds of any one of the formulas disclosed here include hydroxidesof alkali metals, including sodium, potassium, and lithium; hydroxidesof alkaline earth metals, for example, calcium and magnesium; hydroxidesof other metals, for example, aluminum and zinc; ammonia, organicamines, for example, unsubstituted or hydroxyl-substituted mono-, di-,or tri-alkylamines, dicyclohexylamine; tributyl amine; pyridine;N-methyl, N-ethylamine; diethylamine; triethylamine; mono-, bis-, ortris-(2-OH—C₁₋₆ alkyl amine), for example,N,N-dimethyl-N-(2-hydroxyethyl)amine or tri-(2-hydroxyethyl)amine;N-methyl-D-glucamine; morpholine; thiomorpholine; piperidine;pyrrolidine; and amino acids, for example, arginine, lysine, and thelike.

Methods of Making

Any composition described here may be readily prepared by a skilledengineer using methods and apparatuses generally known in chemicalengineering for mixing, suspending and dissolving organic chemicals inan aqueous solvent. For example, a round-bottom mixing tank, a conebottom mixing tank, or a flat bottom chemical mixing tank. A chemicalengineer will also be able to choose tools and instruments for qualitycontrol measurements, for example, monitoring pH, viscosity, density andalso sedimentation and generation of bubbles of gas in the composition.

In some embodiments, preparation of a gas-generating compositionincludes adding an organic amine compound to an aqueous solution, addinga gas-generation compound to the resultant composition, and, ifnecessary, adding an acid or base to adjust pH of the composition to adesired value (for example, pH of about 6 or about 7). In some aspectsof these embodiments, the aqueous solution contains a viscosifier or afoaming surfactant, or both.

In some embodiments, preparation of a gas-generating compositionincludes adding an organic amine compound and a gas generating compound(simultaneously or sequentially) to an aqueous solution, and adjustingpH of the resultant composition to a desired value. In some embodiments,preparation of a gas-generating composition includes adding agas-generating compound to an aqueous solution, adding an acid or baseto adjust pH of the composition to a desired value, adding aminecompound to the resultant composition, and, if necessary, adding anadditional amount of acid or base to adjust pH of the composition to thedesired value. In some aspects of the foregoing embodiments, aqueoussolution contains a viscosifier or a foaming surfactant, or both.

In some embodiments, an oxidizer may be admixed with the gas-generatingcomposition in a wellbore fluid. In these embodiments, the oxidizer maybe added to the composition immediately before using the composition indownhole operations. In one example, the oxidizing agent is added to thewellbore treatment fluid either before or after adding the gasgenerating aqueous composition to the treatment fluid.

Methods of Using

Production of a recoverable fluid from a subterranean formation oftenrequires drilling into the subterranean formation to produce a wellborethrough which the recoverable fluid is brought to the surface. Adrilling fluid is used to aid the drilling of the well by creatinghydrostatic pressure to prevent formation fluid from entering into thewell prematurely, keeping the drill bit cool, and suspending the drillcuttings and carrying them to the surface. Conventional drilling fluidshaving constant density are generally uncompressible and exert aconstant hydrostatic pressure against the wellbore walls. Because ofthis, when conventional fluid is used for drilling, sudden changes information type and formation strength may lead to “kicks” (unexpectedformation fluid influxes to the well), collapse of the bore by pressuredformation fluids, and loss of circulation of the drilling fluid into aparticularly weak formation. Drilling fluid left behind a casing mayalso lead to sustained casing pressure (SCP) or annular pressure buildup (APB) due to thermal expansion of residual drilling fluid left behindcasing, making the casing susceptible to collapse. However, in case of adrilling fluid having significant compressibility, density of the fluidand hydrostatic pressure exerted by the fluid against the formation mayvary depending on the strength of the formation. For instance, theeffective density of drilling fluid and hydrostatic pressure against thewall may increase when the drill bit is cutting through a strong andhard formation. Similarly, effective density of the drilling fluid andconcomitantly hydrostatic pressure against the wellbore wall maydecrease as the drilling occurs in the weaker part of the formation andavoid collapse of the bore or loss of drilling fluid to the formation,or both.

In a general aspect, the present application provides a method of usingan aqueous gas-generating composition of the present disclosure tomodulate density of wellbore fluids. In some embodiments, the methodincludes adding the aqueous gas-generating composition to a wellborefluid to obtain a wellbore fluid with variable density. In someembodiments, volume ratio of the aqueous gas-generating composition tothe wellbore fluid is from about 10:1 to about 1:10, from about 8:1 toabout 1:8, from about 5:1 to about 1:5, from about 3:1 to about 1:3,from about 2:1 to about 1:2, or from about 1:1 to about 1:2. In someembodiments, volume ratio of the aqueous gas-generating composition tothe wellbore fluid is about 5:1, about 3:1, about 2:1, about 3:2, about1:1, about 2:3, about 1:2, about 1:3, or about 1:5.

In some embodiments, an amount of gas-generating compound (for example,azo compound) in the wellbore fluid with variable density is from about0.1 wt. % to about 10 wt. %, from about 0.2 wt. % to about 8 wt. %, fromabout 0.5 wt. % to about 5 wt. %, from about 1 wt. % to about 4 wt. %,or from about 1 wt. % to about 3 wt. % based on the weight of thewellbore fluid. In some embodiments, an amount of gas-generatingcompound in wellbore fluid with variable density is about 0.5 wt. %,about 1 wt. %, about 1.5 wt. %, about 2 wt. %, about 3 wt. %, about 4wt. %, or about 5 wt. % based on the weight of the wellbore fluid.

In some embodiments, an amount of foaming surfactant is the wellborefluid with variable density is from about 1 wt. % to about 20 wt. %,from about 2 wt. % to about 15 wt. %, or from about 5 wt. % to about 10wt. % based on the weight of the wellbore fluid. In some embodiments, anamount of foaming surfactant is the wellbore fluid with variable densityis about 3 wt. %, about 5 wt. %, about 6 wt. %, about 8 wt. %, about 10wt. %, about 12 wt. %, or about 15 wt. % based on the weight of thewellbore fluid.

In some embodiments, adding the gas-generating composition to thewellbore fluid, for example, a cement slurry, drilling fluid,stimulation fluid, clean-up fluid, fracturing fluid, completion fluid,remedial treatment fluid, cementing fluid, or carrier fluid, increasescompressibility of the fluid. In some embodiments, increasedcompressibility leads to variable density of the fluid. In someembodiments, variable density of a wellbore fluid leads to wellborestability and smooth operation. Wellbore fluids with variable densityand increased compressibility include drilling fluids, carrier fluids,fracturing fluids, spotting fluids, cementing fluids, completion fluids,stimulation fluids, remedial fluids and clean-up fluids.

In some embodiments, variable density is achieved by activating a gasgenerating compound in the wellbore fluid to produce gaseous compounds(for example, bubbles of gas). Without being bound to any particulartheory, it is believed that gases are more compressible than pureliquids. Hence, when bubbles of gas are dispersed in the liquid carrier,the resultant composition is more compressible than the pure liquidcarrier without any gas dispersed in it.

In some embodiments, the gas-generating compound in the wellbore fluidmay be activated by temperature in the wellbore (for example, anytemperature in the wellbore greater than 100° C.). In some embodiments,the gas generating compound in the wellbore fluid may be activated bybasic pH (for example, a pH of about 7.5, about 8, about 9, about 10,about 11, or about 12). For example, a gas-generating compound may beactivated to produce gas when an aqueous gas-generating composition isadded to a wellbore fluid having pH of about 12, and the resultantwellbore fluid containing the gas-generating compound has pH of about 5,about 6, about 7, about 9, or greater. In some embodiments, a solutionof a base, for example, NaOH may be added to the wellbore fluidconsecutively or concurrently with the aqueous gas-generatingcomposition to achieve the desired pH value in the wellbore fluid (forexample, a pH of about 5, about 6, about 7, about 9, about 11, or about12). In some embodiments, aqueous gas-generating composition asdescribed earlier may be prepared beforehand and safely stored beforeapplication (for example, the gas-generating composition may be producedat a dedicated production facility and transported to the wellbore sitefor application). In other embodiments, a gas-generating composition maybe prepared immediately before application, for example, by a mudengineer, from the individual components. In some embodiments, anoxidizing compound may be added to the wellbore fluid consecutively orconcurrently with the aqueous gas-generating composition. In someembodiments an oxidizing compound may be added to the aqueousgas-generating composition immediately before admixing the compositionwith the wellbore fluid. In such embodiments, the gas generatingcomposition and the oxidizing compound may be stored or transported tothe wellbore application site separately. In some embodiments, anaqueous gas-generating compound is admixed with the wellbore fluid atthe application site, for example, using a mixer tank. In someembodiments, a liquid injection pump is utilized to inject thegas-generating composition into a wellbore treatment fluid on-the-fly ina continuous operation. In some embodiments, an oxidizer compound isbatch mixed with the gas-generating composition or with the wellborefluid on site. In some embodiments, the oxidizing compound is injecteddownhole using a liquid injection pump. In some embodiments, the gasgeneration is activated by any of the aforementioned activation factors,or any combination thereof. In some embodiments, gas generation isactivated by pH of the wellbore fluid greater than 5 (for example, pHgreater than 6, greater than 7, or greater than 8) and by temperature inthe wellbore greater than 100° C.

The methods described earlier advantageously allow for introducing anamount of gas to the wellbore fluid. In some embodiments, volumefraction of gas in the wellbore fluid generated by the presentcomposition is from about 0.1 v/v % to about 50 v/v %, from about 1 v/v% to about 25 v/v %, or from about 1 v/v % to about 10 v/v % based onthe amount of the wellbore fluid.

Controlled compressibility may be also desired in wellbore set cementapplications. In primary cementing, inclusion of an amount of gas in thecement mixture may be advantageous for improved resiliency and reducedbrittleness of set cement. In one aspect, the present applicationprovides a method of using an aqueous gas-generating composition of thepresent disclosure to modulate density of set cement. In someembodiments, the method includes adding an aqueous gas-generatingcomposition to the cement mixture prior to pumping the cement mixturedownhole. In some embodiments, the method includes injecting the aqueousgas-generating composition downhole to mix with the cementing mixture.In some embodiments, the gas-generating compound is activated before thecement sets. In such embodiments the set cement includes bubbles of gas.Without being bound to any particular theory, it is believed thatbubbles of gas in set cement provide increased compressibility to thecement. This is advantageous, because in an event of sudden pressureincrease, set cement will not collapse but rather compress the bubblesof gas in the cement material in an elastic manner.

EXAMPLES

Materials and General Methods

Aqueous solutions xanthan, diutan and vinylphosphonate-graftedhydroxycellulose (HEC) were employed as simulated wellbore fluids.Sodium dodecyl sulfate (sodium lauryl sulfate) and hydroxysulfobetaine(aqueous solution) were employed as representative foaming surfactants.

Example 1

1.5 g of azodicarbonamide solid were added to 50 milliliters of 0.8%xanthan solution and stirred vigorously for an hour to obtain awell-dispersed stable suspension. 10 ml (containing 0.3 g ofazodicarbonamide) of the suspension was added to several graduatedcylinders. Then, foaming surfactants and amine activators were added, asspecified in Table 1. The suspension was stirred and the cylinders werekept in a water bath heated to 140° F. The initial fluid volume beforemeasurements was 12 ml. The gas volumes were measured periodically. Theresults are shown in Table 1.

TABLE 1 A¹ B² C³ D⁴ pH E⁵ F⁶ G⁷ H⁸ Foam stability None 0.4Carbohydrazide  0.3 g 7.0 50 58 79 160 Slightly heterogeneous bubblesizes 0.15 0.4 Carbohydrazide  0.3 g — 55 58 79 160 Stable, homogeneousbubbles 0.15 None Carbohydrazide  0.3 g — 58 28 62  32 Unstable foamNone 0.4 Toluene sulfonyl  0.5 g 6.8 12 12  0  0 No foam semicarbazide0.15 0.4 Toluene sulfonyl  0.5 g — 12 12  0  0 semicarbazide 0.15 0.4 mlToluene sulfonyl 0.45 g — 32 44 73 107 hydrazide 0.15 0.4 TEPA 0.15 ml —33 40 70  93 0.15 0.4 TEPA  0.3 ml — 40 46 74 113 0.15 0.4 TEPA 0.45 ml— 45 48 75 120 0.15 0.4 Ethylene diamine  0.3 ml — 56 63 81 170 0.15 0.4Triethanolamine  0.4 ml — 18 23 48  37 0.15 0.4 Carbohydrazide +  0.3g + — 14 14 21  10 Note: No Potassium persulfate 0.35 g azodicarbonamidewas used in this experiment 0.15 0.4 Carbohydrazide +  0.3 g + — 60 6481 173 Potassium persulfate  0.3 g 0.15 0.4 Magnesium oxide 0.35 g — 2333 64  70 ¹lauryl sulfate, g. ²hydroxysultaine, ml. ³activator (amine orinorganic compound) ⁴activator amount ⁵volume in 1 hour and 30 min, ml.⁶volume in 3 hours, ml. ⁷% gas in fluid after 3 hours. ⁸gas amount, ml/gof azo compound at 140° F.The results of Example 1 are discussed later with the results of Example2.

Example 2

The results for diutan solutions are shown in Table 2. In a typicalprocedure, 0.5% by volume of diutan solution in water was employed.Azodicarbonamide was added with vigorous stirring, which was continueduntil all the solid was uniformly dispersed and suspended. In a typicalexperiment, 0.5 g azodicarbonamide was suspended in 10 ml of diutansolution, followed by addition of foaming surfactant (sodium laurylsulfate, 0.4 ml), and the activator. The gas measurements were made atroom temperature. The starting volume of the fluid in each experimentwas 12 ml.

TABLE 2 A¹ B² C³ D⁴ E⁵ F⁶ G⁷ DETA 0.5 ml n.d., 20   40 ml/26 hrs 40   56 (in 26 hrs) Carbohydrazide 0.5 g 17 17 >80 ml 29 >136 (in 48 hrs)NaOH (solid) 0.5 g 20 25 >80 ml 52 >136 (in 48 hrs) ¹activator²activator amount ³fluid volume in 60 min, ml. ⁴fluid volume is 100 min,ml. ⁵final volume after 48 hours, ml (estimated) ⁶% gas in 100 min ⁷gasamount ml/g of azo compound at room temperature

The results of Examples 1 and 2 show that (1) organic amines areeffective activators, and generally perform better than inorganic oxides(for example, MgO experiment in Table 1); (2) low pH values, forexample, less than pH of 9, can be employed to generate nitrogen gasfrom the azo compound; and (3) oxidizing agents are optional (notneeded) to generate nitrogen gas from the azo compounds.

Other Embodiments

It is to be understood that while the present application has beendescribed in conjunction with the detailed description thereof, theforegoing description is intended to illustrate and not limit the scopeof the present application, which is defined by the scope of theappended claims. Other aspects, advantages, and modifications are withinthe scope of the following claims.

What is claimed is:
 1. A storable gas-generating aqueous compositioncomprising an azo compound of Formula (I):

or a salt thereof, where: X¹ and X² are each independently selected fromthe group consisting of C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, OR^(a1),and NR^(c1)R^(d1); each R^(a1), R^(c1), and R^(d1) is independentlyselected from the group consisting of H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆alkynyl, C₃₋₇ cycloalkyl, and C₆₋₁₀ aryl; and an organic amine, whereinthe gas-generating composition has a pH of between about 4 and about 9,and wherein the molar ratio between the azo compound and the organicamine is between 1:10 and 1:1; and a viscosifier added to the storablegas-generating aqueous composition, wherein the viscosifier comprisesxanthan, diutan, or vinylphosphonate-grafted hydroxycellulose (HEC), orany combinations thereof.
 2. The composition of claim 1, where: X¹ andX² are each independently selected from the group consisting of OR^(a1)and NR^(c1)R^(d1); and each R^(a1), R^(c1) and R^(d1) is independentlyselected from the group consisting of H and C₁₋₆ alkyl.
 3. Thecomposition of claim 2, where the azo compound is azodicarbonamide:

or a salt thereof.
 4. The composition of claim 1, where an amount of theazo compound in the aqueous composition is from about 1 wt. % to about10 wt. %.
 5. The composition of claim 1, where the organic amine is aprimary, secondary or tertiary amine of Formula (IVa):

or a salt thereof, where: R^(n1), R^(n2) and R^(n3) are independentlyselected from the group consisting of H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl,and 4-7 membered heterocycloalkyl, each of which is optionallysubstituted with 1, 2, or 3 substituents independently selected from thegroup consisting of hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino,di(C₁₋₆ alkyl)amino, carboxy, and carbamyl; or any two R^(n1) andR^(n2), or any two R^(n2) and R^(n3), or any two R^(n1) and R^(n3)together with the N atom to which they are attached form a 4-7 memberedheterocycloalkyl, which is optionally substituted with 1, 2, 3, 4, or 5substituents independently selected from the group consisting of C₁₋₆alkyl, NH₂—C₁₋₆ alkylene, OH—C₁₋₆ alkylene, hydroxyl, C₁₋₆ alkoxy,amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and carbamyl. 6.The aqueous composition of claim 5, where: R^(n1), R^(n2) and R^(n3) areindependently selected from the group consisting of H and C₁₋₆ alkyl,which is optionally substituted with 1, 2, or 3 substituentsindependently selected from the group consisting of hydroxyl, C₁₋₆alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, and carboxy.
 7. Thecomposition of claim 1, where the organic amine is a hydrazine compoundof Formula (IVb):

or a salt thereof, where: R^(n4), R^(n5), R^(n6), and R^(n7) areindependently selected from the group consisting of H, C₁₋₆ alkyl, C₃₋₇cycloalkyl, and 4-7 membered heterocycloalkyl, each of which isoptionally substituted with 1, 2, or 3 substituents independentlyselected from the group consisting of hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆alkylamino, di(C₁₋₆ alkyl)amino, carboxy, and carbamyl; or any twoR^(n4) and R^(n5), or any two R^(n6) and R^(n7), together with the Natom to which they are attached form a 4-7 membered heterocycloalkyl,which is optionally substituted with 1, 2, 3, 4, or 5 substituentsindependently selected from the group consisting of C₁₋₆ alkyl,hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy and, carbamyl.
 8. The aqueous composition of claim 7, whereR^(n4), R^(n5), R^(n6), and R^(n7) are independently selected from thegroup consisting of H and C₁₋₆ alkyl, which is optionally substitutedwith 1, 2, or 3 substituents independently selected from the groupconsisting of hydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆alkyl)amino, and carboxy.
 9. The composition of claim 1, where theorganic amine is an ethyleneimine compound of Formula (IVc):

or a salt thereof, where: n is an integer from 1 to 10, R^(n8), R^(n9),R^(n10), and R^(n11) are independently selected from the groupconsisting of H, C₁₋₆ alkyl, C₃₋₇ cycloalkyl, and 4-7 memberedheterocycloalkyl, each of which is optionally substituted with 1, 2, or3 substituents independently selected from the group consisting ofhydroxyl, C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, and carbamyl; or any two R^(n8) and R^(n9), or any two R^(n10)and R^(n11), together with the N atom to which they are attached form a4-7 membered heterocycloalkyl, which is optionally substituted with 1,2, 3, 4, or 5 substituents independently selected from the groupconsisting of C₁₋₆ alkyl, NH₂—C₁₋₆ alkylene, OH—C₁₋₆ alkylene, hydroxyl,C₁₋₆ alkoxy, amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino, carboxy, andcarbamyl.
 10. The composition of claim 9, where n is an integer from 1to 8, and R^(n8), R^(n9), R^(n10) and R^(n11) are independently selectedfrom the group consisting of H and C₁₋₆ alkyl, which is optionallysubstituted with 1, 2, or 3 substituents independently selected from thegroup consisting of amino, C₁₋₆ alkylamino, di(C₁₋₆ alkyl)amino,carboxy, and carbamyl.
 11. The composition of claim 1, where the organicamine is a hydrazide compound of Formula (IIa) or Formula (IIb):

or a salt thereof, where: R¹ is selected from the group consisting of H,C₁₋₆ alkyl, C₆₋₁₀ aryl, and —NH—NH₂, where said C₆₋₁₀ aryl is optionallysubstituted with 1, 2, or 3 substituents independently selected from thegroup consisting of C₁₋₆ alkyl, hydroxyl, amino, C₁₋₆ alkoxy, and NO₂;and R² is selected from the group consisting of H, C₁₋₆ alkyl, carboxy,carbamyl, C₁₋₆ alkylcarbamyl, di(C₁₋₆-alkyl)carbamyl, aminosulfonyl,C₁₋₆ alkylaminosulfonyl, and di(C₁₋₆ alkyl)aminosulfonyl.
 12. Thecomposition of claim 11, where: R¹ is selected from the group consistingof C₆₋₁₀ aryl and —NH—NH₂, where said C₆₋₁₀ aryl is optionallysubstituted with 1, 2, or 3 substituents independently selected from thegroup consisting of C₁₋₆ alkyl and NO₂; and R² is selected from thegroup consisting of H, carboxy, carbamyl, and aminosulfonyl.
 13. Thecomposition of claim 1, where the organic amine is selected from thegroup consisting of: carbohydrazide, p-toluenesulfonyl hydrazide,hydrazine, triethanolamine, ethylene diamine, tetraethylene pentamine(TEPA), diethyletriamine (DETA), triethylenetetramine (TETA), andpolyethyleneimine, or a salt thereof.
 14. The composition of claim 1,where an amount of the organic amine in the composition is from about 1wt. % to about 10 wt. %.
 15. The composition of claim 1, where theviscosifier comprises from 0.1 wt. % to 1 wt. % of the composition. 16.The composition of claim 1, comprising a foaming surfactant.
 17. Thecomposition of claim 16, wherein the foaming surfactant comprises 1 wt.% to 5 wt. % based on the weight of the aqueous composition.
 18. Awellbore fluid comprising the composition of claim 1.